BTS Clinical Statement on air travel for passengers with respiratory disease

BTS Clinical Statement on air travel for passengers

with respiratorydisease

Robina Kate Coker,

Alison Armstrong,

Alistair Colin Church,

Steve Holmes,

Jonathan Naylor,

Katharine Pike,

Peter Saunders,

Kristofer John Spurling,

Pamela Vaughn

INTRODUCTION

BTS recommendations for managing passengers

with stable respiratory disease planning air travel

were published in Thorax in 2011.

This followed

original guidance published in 2002

and an online

update in 2004.

The 2011 recommendations

provided an expert consensus view based on litera-

ture reviews, aimed at providing practical advice for

lung specialists in secondary care. Recognising that

knowledge in this area has grown since 2011, and

that updated, pragmatic advice regarding which

respiratory patients need specialist assessment is

required, the Society has commissioned a new clin-

ical statement.

Although air travel appears generally safe for

those with respiratory disease assessed previously

by a lung specialist,

a decision to undertake air

travel should not be taken lightly. Diverted flights

incur significant expense and inconvenience, and a

patient whose condition deteriorates during flight

can pose huge challenges to airline crew and other

passengers. High altitude destinations may also be

problematic.

European and North American regulatory

authorities limit maximum cabin altitude to 2438 m

(8000 ft) under normal operating conditions.

5–7

The choice of 2438 m was based on the oxyhae-

moglobin dissociation curve, which shows that

up to this level arterial oxygen saturations (SaO

)

remain >90% in the average healthy individual.

Some newer commercial aircraft have a lower

normal cabin altitude, for example, the Boeing 787

Dreamliner. However, passengers booking such

flights should note that airlines may, for operational

reasons, switch at short notice to an aircraft with a

higher normal cabin altitude.

Besides the passenger’s respiratory condition and

significant comorbidities, a decision regarding suit-

ability for air travel should consider flight duration

and timings, destination (especially if at altitude

or subject to extreme weather conditions), equip-

ment and medications, and whether equipment will

operate effectively and safely at altitude.

There have been developments in three key

areas over the last decade. The first is an attempt,

with research from several groups, to define more

precisely the value and role of the hypoxic challenge

test (HCT). This has included examining the accu-

racy of other, more routinely available lung func-

tion parameters, in predicting hypoxaemia during

air travel. HCT can be expensive in terms of equip-

ment and consumables; and demands additional

staff time. A ‘negative’ HCT (where in- flight

oxygen is not considered necessary) takes around

30 min; if oxygen titration is needed it takes around

60 min. In contrast, spirometry requires 20 min, a

walk test 30 min, and ‘full’ lung function testing

45 min.

Results of such assessments may already be

available as part of routine clinical care.

The second development has been increasing

recognition that, although early research in this

area focused on patients with chronic obstructive

pulmonary disease (COPD), other patient groups

may respond differently to altitude- related hypox-

aemia. Although data remain limited, available

evidence no longer appears to support a ‘one size

fits all’ approach.

Finally, the equipment used to deliver oxygen

has changed significantly over the last decade,

with much greater availability of portable oxygen

concentrators (POCs). For overseas travel, patients

usually need to lease a POC privately, since UK

companies do not generally allow their equipment

to be taken out of the country. If a POC is to be used

in- flight, the equipment must be approved by the

airline before travel. There are now a wide variety

of such devices, providing varying flow rates and

modes of delivery (continuous flow vs pulse- dose),

and not all are suitable for all individual patients.

Attention has, therefore, been drawn in this State-

ment to newer data, especially those published since

the 2011 BTS recommendations.

Readers wanting

more detailed background information on physi-

ology and the flight environment should consult the

2002 and 2011 BTS documents.

1 2

Scope

The clinical statement provides practical advice for

healthcare professionals in primary and secondary

care managing passengers with pre- existing respi-

ratory conditions planning commercial air travel,

including those recovering from an acute event/

exacerbation. It provides information for patients

and carers; and is also intended to be helpful to

patient support groups, airlines and associated

medical services. Passengers returning home with a

new diagnosis should be reviewed in the light of the

presenting condition and individual circumstances.

The document does not cover emergency aero-

medical evacuation, or travel on non- commercial

flights. Pregnant passengers with respiratory disease

should also consult Royal College of Obstetricians

and Gynaecologists guidance (see online supple-

mental appendix 1).

BTS Clinical Statement

To cite: CokerRK,

ArmstrongA, ChurchAC,

etal. Thorax Epub ahead of

print: [please include Day

Month Year]. doi:10.1136/

thoraxjnl-2021-218110

► Additional supplemental

material is published online

only. To view, please visit the

journal online (http:// dx. doi.

org/ 10. 1136/ thoraxjnl- 2021-

218110).

Respiratory Medicine,

Hammersmith Hospital, Imperial

College Healthcare NHS Trust,

London, UK

The Newcastle upon Tyne

Hospitals NHS Foundation Trust,

Newcastle upon Tyne, UK

Scottish Pulmonary Vascular

Unit, Golden Jubilee Hospital,

Clydebank, UK

The Park Medical Practice,

Shepton Mallet, UK

Queen Elizabeth Hospital,

Birmingham, UK

Department of Paediatric

Respiratory Medicine, Bristol

Royal Hospital for Children,

Bristol, UK

Churchill Hospital, Oxford, UK

Respiratory Physiology

Department, North Middlesex

University Hospital, London, UK

Glasgow Royal Inﬁrmary,

Glasgow, UK

Correspondence to

Dr Robina Kate Coker,

Respiratory Medicine,

Hammersmith Hospital, Imperial

College Healthcare NHS Trust,

London, London, UK;

robina. coker@ imperial. ac. uk

employer(s)) 2022. Re- use

permitted under CC BY- NC. No

commercial re- use. See rights

and permissions. Published

by BMJ.

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BTS Clinical Statement

The Statement addresses adults and children with the following

conditions or undergoing the following procedures:

► Airflow obstruction including asthma and COPD.

► Bronchopulmonary dysplasia.

► Cystic fibrosis (CF).

► Non- CF bronchiectasis.

► Restrictive respiratory disease including interstitial lung

disease (ILD), respiratory muscle and chest wall disorders.

► Thoracic surgery or other interventional procedures.

► Pleural disease including pneumothorax and pleural effusion.

► Respiratory infections.

► Obstructive sleep apnoea syndrome (OSAS) and obesity

hypoventilation syndrome (OHS).

► Venous thromboembolism (VTE).

► Pulmonary hypertension (PH).

► Lung cancer and mesothelioma.

► Hyperventilation and dysfunctional breathing (DB).

Preflight assessment is described. Appendix A provides infor-

mation on logistics for air travel with equipment (nebulisers,

oxygen and ventilators); Appendix B provides technical infor-

mation for respiratory physiologists. Sources of useful informa-

tion, Information for primary care healthcare practitioners and

for patients are provided in online supplemental appendices 1–3.

Heart disease and HIV are excluded, as are emergency repa-

triation and travel on military or other non- commercial flights

including helicopter travel. The Terrence Higgins Trust and

British Heart Foundation provide advice on travel with HIV and

heart conditions respectively (see online supplemental appendix

1).

METHODOLOGY

Dr Robina Coker chaired the clinical statement group (CSG).

Membership was drawn from respiratory medicine, paediat-

rics, nursing, respiratory physiology, physiotherapy and primary

care. The CSG identified key areas requiring Clinical Practice

Points. The group reviewed previous BTS recommendations on

this topic

1–3

and supplemented the evidence with up- to- date

literature searches. The overall content was developed to reflect

the scope approved by the BTS Standards of Care Committee

(SOCC). Following discussions of broad statement content, indi-

vidual sections were drafted by group members. A final edited

draft was reviewed by the BTS SOCC before posting for public

consultation and peer review on the BTS website in January

2020. The document was revised in the light of consultation

feedback and approved by the BTS Standards of Care Committee

in July 2021 before final publication.

Summary of clinical practice points

Preﬂight screening

► All patients should undergo careful initial evaluation with

history and physical examination by a clinician who is

competent. The history should include:

– Review of symptoms, baseline exercise capacity, recent

exacerbation history, treatments and previous experience

of air travel.

– Consideration of the logistics of the intended journey, to

include (if known):

– Number and duration of flights, including whether

daytime or overnight,

– Location of stop- over(s) and destination: these deter-

mine air quality, altitude and available medical facil-

ities,

– Time away from home

– Return journey.

► Further assessment by a respiratory specialist is advised for

those in whom screening raises concerns, and HCT may be

advised.

The following clinical practice points are speciﬁc to infants and

children

► For infants born at term (>37 weeks) it is prudent to delay

flying for 1 week after birth to ensure they are healthy.

► Infants born prematurely (<37 weeks) with or without a

history of respiratory disease who have not reached their

expected date of delivery at the time of flying should have

in- flight oxygen available. HCT may not be a reliable guide

of oxygen requirement in this group. If air travel is essential,

they should travel with oxygen at a tolerable low flow, recog-

nising that this may be a minimum of 1 L/min depending on

equipment.

► Infants under 1 year with a history of chronic respiratory

problems should be discussed with a respiratory paediatri-

cian and HCT considered. Those with SpO

<85% on HCT

should have in- flight oxygen available; paediatrician discre-

tion should be used for infants with SpO

85%–90% recog-

nising that sleep or respiratory infection may further reduce

saturations in this group.

► In children with chronic lung disease able to perform

spirometry whose forced expiratory volume in 1 s (FEV

) is

consistently <50% predicted, HCT should be considered.

This includes children with CF and primary ciliary dyski-

nesia (PCD). Children with chronic lung disease who are too

young to perform spirometry reliably should have a clinical

assessment of disease severity and their likely tolerance of

hypoxia. In children with CF the disease is rarely severe

enough to compromise lung function significantly at this

age.

► Infants and children who have required long- term oxygen

in the last 6 months should be discussed with a respiratory

paediatrician and HCT considered.

Patient selection for HCT

See figures 1 and 2.

The following patients should not require HCT

► Those with stable disease who have previously undergone

HCT (no recent hospital admissions, exacerbations, or

significant changes to treatment).

► Patients with COPD with baseline SpO2 ≥95% and either

MRC score 1–2 or desaturation to no less than 84% during

6 min walk test (6MWT) or shuttle walking test (SWT),

should be able to travel without in- flight oxygen.

► Those with previous significant intolerance to air travel,

such as mid- air emergency oxygen or diversion. These

should have in- flight oxygen available at 2 L/min provided

there is no history of hypercapnia.

► Preterm infants who have not reached their due date at the

time of travel, as testing is not a reliable guide of oxygen

requirement in these infants. These should have in-ﬂight

oxygen available, delivered at 1–2 L/min if they develop

tachypnoea, recession, or other signs of respiratory distress.

HCT should be considered for the following patients

► Patients with COPD with resting SpO

≤95%, MRC score 3

or greater, or desaturation to <84% on 6MWT or SWT, and

in whom there are concerns about hypercapnia.

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BTS Clinical Statement

► Infants and children with a history of neonatal respiratory

problems, or existing severe chronic lung disease including

those with FEV1 persistently <50% predicted.

► Adults and children with severe asthma, evidenced by

persistent symptoms and/or frequent exacerbations despite

optimal treatment regardless of resting sea level SpO

► Patients with ILD in whom SpO

falls to <95% on exercise,

and whose resting sea level arterial oxygen tension (PaO

)

is ≤9.42 kPa or whose TLCO is ≤50%.

► Those with severe respiratory muscle weakness or chest wall

deformity in whom forced vital capacity (FVC) is <1 L.

► Those with existing or previous hypercapnia and those at

risk of hypercapnia, including those taking medication(s)

which can cause respiratory depression.

► Patients with a history of type 2 respiratory failure already

on LTOT at sea level. However, if there is no evidence of

hypercapnia, it seems reasonable to recommend an increase

in flow rate by 2 L/min in- flight, provided the equipment can

provide it (see Appendix A)

HCT results

► PaO

≥6.6 kPa (≥50 mm Hg) or SpO

≥85%: in- flight

oxygen not required.

► PaO

<6.6 kPa (<50 mm Hg) or SpO

<85%: in- flight

oxygen recommended.

► Where required, titrate oxygen to maintain PaO

≥6.6 kPa

or SpO

≥85% in adults, SpO

90% in children aged 1 year

or more.

Asthma

► The patient’s condition should be optimised before travel,

with attention paid to inhaler technique and smoking cessa-

tion referral as required.

► All medications and spacer devices should be carried in

hand luggage to mitigate the risk of lost or missing hold

baggage.

► Emergency medications, including salbutamol inhalers and

spacers, must be immediately accessible.

► Individuals prescribed epinephrine auto- injectors should

have them readily available.

► For acute exacerbations on board, the passenger’s own

bronchodilator inhaler should be given, with a spacer if

needed.

► The passenger should alert the cabin crew if symptoms do

not respond rapidly to use of the inhaler, or if they recur

after a short interval.

Figure 1 Preﬂight assessment of patients with chronic airﬂow obstruction.

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BTS Clinical Statement

► If the passenger does not have their own inhaler with them,

or if it is inaccessible, the airline may carry an inhaler in the

emergency medical kit. Spacers are not commonly available.

► Those with severe asthma should consult their respiratory

specialist beforehand and consider taking an emergency

supply of oral corticosteroid in their hand luggage in addi-

tion to their usual medication.

► Passengers with severe asthma are advised to carry copies of

their asthma management plan and/or relevant clinic letters.

Information can be held securely as scanned copies on a

mobile phone, or on a digital platform such as the National

Health Service (NHS) App.

► Food allergy affects up to 8.5% of children and adults with

asthma and asthma is a risk factor for severe or fatal anaphy-

laxis. Appropriate precautions for those affected include

wiping tray tables and hands, informing the airline before-

hand and the cabin crew of allergies, and not eating during

flights or bringing known ‘safe’ foods from home.

Chronic obstructive pulmonary disease

► The patient’s condition should be optimised before travel,

with attention paid to inhaler technique and smoking cessa-

tion referral where appropriate.

► All medications and spacer devices should be carried in hand

luggage to mitigate the risk of missing hold baggage.

► Emergency medications, including salbutamol inhalers and

spacers, must be immediately accessible.

► For acute exacerbations on board, the passenger’s own bron-

chodilator inhaler should be given, with a spacer if appropriate.

► Passengers with severe COPD are advised to carry a copy of

their COPD management plan and/or relevant clinic letters.

This information can be held securely as scanned copies on

their mobile phone A history of previous pneumothorax or

bullous lung disease necessitates assessment by a respiratory

specialist to determine the potential risk of complications

from reduced cabin pressure.

Figure 2 Preﬂight assessment of patients with restrictive respiratory disease.

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BTS Clinical Statement

► Patients with COPD are at greater risk of VTE as a direct

consequence of the underlying condition, as well as after an

exacerbation. They should be advised accordingly, especially

if planning longer flights when the risk is further enhanced.

► Patients requiring long- term oxygen therapy should also

plan for oxygen supplementation at their destination (see

online supplemental appendix 1).

► Wherever possible, those who have had a recent exacerba-

tion of their condition should not fly until their condition

is stable and use of reliever therapy has returned to their

usual baseline. If their condition deteriorates while overseas,

medical advice should be sought before undertaking the

return flight.

Cystic ﬁbrosis

► All medications and spacer devices should be carried in hand

luggage to mitigate the risk of missing hold baggage.

► Patients with CF under the age of 6 are likely to be well

enough to fly at the paediatrician’s discretion.

► In those with CF who are old enough for spirometry and

whose FEV1 is <50% predicted, HCT is recommended.

If SpO2 falls below the 90% cut- off, as outlined above,

in- flight oxygen is advised.

► In children with chronic lung disease able to perform

spirometry whose FEV

is consistently <50% predicted,

HCT should be considered. This includes children with

CF and non- CF bronchiectasis. Children with chronic lung

disease who are too young to reliably perform spirometry

should have a clinical assessment of assess disease severity

and their likely tolerance of hypoxia. For children with CF

disease is rarely severe enough to severely compromise lung

function at this age.

Non-CF bronchiectasis

► Regular airway clearance is essential for those dealing with

overproduction of mucus.

► Advice from a respiratory physiotherapist on adapting

airway clearance techniques should be sought for long- haul

flights.

► Portable nebulisers and positive expiratory pressure (PEP)

devices may be considered, but use of these devices in- flight

must be approved by the airline before travel.

Interstitial lung disease

► In patients with comorbidity, including PH and/ or cardio-

vascular disease, attention should also be paid to the impact

of air travel on these conditions.

► Physicians may wish to consider HCT in those whom

SpO2 falls to <95% on exercise, and/or in those in whom

either Transfer Factor Carbon Monoxide (TLCO) ≤50% or

PaO

≤9.42 kPa (if available).

► Patients with TLCO <50% of predicted or PaO

≤9.42 kPa

are likely to need in- flight oxygen. If there are no concerns

about hypercapnia it may be reasonable to recommend 2 L/

min without recourse to HCT. In those in whom there are

concerns about CO2 retention, titration HCT is advised to

determine the oxygen flow rate.

Thoracic surgery

► The opinion of the surgeon or interventionalist should be

obtained before the patient travels by air. Patients, profes-

sionals and their carers should be aware that this may result

in a delay of 4 weeks for non- essential air travel and 2 weeks

for essential air travel.

► Careful clinical assessment of the patient is required. This

should include consideration of their baseline status including

comorbidities, SpO2, postprocedure complications such as

infection and/or pain, flight duration and destination.

Other interventional procedures

► The opinion of the interventionalist should be obtained

before the patient travels by air.

► Careful clinical assessment of the patient is required. This

should include consideration of baseline status including

co- morbidities, SpO2, postprocedure complications such as

infection or pain, flight duration and destination.

► Patients with no pneumothorax seen on the postprocedure

chest X- ray should wait for 1 week before air travel.

► Patients with a pneumothorax seen on the post- procedure

chest X- ray should wait for one1 week after resolution on

chest X- ray before air travel.

Trapped lung

► The opinion of the interventionalist should be obtained

before the patient travels by air.

► Patients should be assessed carefully and advised on a case-

by- case basis.

► Patients should be clinically stable before air travel.

Bronchoscopic procedures

► The opinion of the interventionalist should be obtained

before the patient travels by air.

► Patients should be clinically stable before they travel.

► After interventional bronchoscopy including Transbronchial

Needle Aspiration (TBNA), Transbronchial Lung Biopsy

(TBB), Endobronchial Ultrasound Bronchoscopy (EBUS)

and endobronchial valve insertion, those with no pneumo-

thorax seen on the postprocedure chest X- ray should wait

for 1 week before air travel.

► After interventional bronchoscopy including TBNA, TBB

and EBUS, those with a pneumothorax seen on the post-

procedure chest X- ray should wait for 1 week after resolu-

tion on chest X- ray before air travel.

Pneumothorax

► Passengers should not travel by air until 7 days after full reso-

lution on chest X- ray.

► Those at higher risk of recurrent pneumothorax should be

advised accordingly.

► Higher- risk groups, including those with cystic lung disease

such as lymphangioleiomyomatosis (LAM) and Birt- Hogg-

Dubé (BHD) syndrome, should be advised accordingly.

► Patients with trapped lung and a chronic air space thought

to present a low risk should be evaluated in secondary care

before travel.

Upper respiratory infection including otitis media and sinusitis

► In passengers who develop sinus barotrauma after flying, it

may be helpful to consider topical and oral decongestants as

well as appropriate analgesia. Prolonged use of decongest-

ants is not advised owing to the risk of rebound congestion

on withdrawal.

► If there is an allergic component, intranasal steroids used

for a week prior to travel, and/or oral corticosteroids may

be considered.

► Symptoms and signs of barotrauma should have resolved

before flying again. This usually takes between 1 and 6 weeks.

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BTS Clinical Statement

► After an episode of acute otitis media, patients are usually

advised not to fly for 2 weeks.

Viral infections

► Patients with highly contagious infections including measles,

chickenpox, mumps, SARS, Middle East respiratory

syndrome (MERS) or COVID- 19 should not be allowed to

travel until they are considered non- infectious.

► Passengers should familiarise themselves with current

national and international regulations regarding air travel,

which should always be observed.

Tuberculosis

► Smear positive patients must not fly until they have provided

two smear negative samples on treatment.

► Those starting treatment for pulmonary tuberculosis (TB),

where not all the information is yet available, should not

travel by air for the first 2 weeks.

► For those who are smear negative and have a fully sensitive

organism, treatment would be expected to render them non-

infectious after 2 weeks.

► For patients with multidrug resistant/extensive drug resistant

(MDR/XDR) TB, travel is prohibited until two negative

culture samples have been produced and there is clinical

evidence of improvement on treatment.

► Extrapulmonary TB does not usually warrant additional

precautions before air travel.

Pneumonia

► All but essential travel should be postponed for 7 days in

those who have reduced baseline sea level SpO2 (<94%).

Obstructive Sleep Apnoea (OSAS) and Obesity Hypoventilation

Syndrome (OHS)

► Daytime flights are advised wherever possible.

► The patient should be advised to carry their continuous posi-

tive airway pressure (CPAP) device as hand luggage, and a

hospital letter to advise that the patient uses CPAP.

► Careful planning and preparation are required, and use of

the patient’s own CPAP device is advised.

► Alcohol and sedatives should be avoided in the 12 hours

before, and during, airline travel.

► Patients should use their CPAP device on board if they are

travelling overnight, and avoid sleeping during daytime

flights.

► Consideration should be given to device settings and whether

adjustment is required for operation at altitude.

► Airline approval for carriage and use of device, including

battery specification, must be gained before travel.

► Consideration should be given to the whole journey. If

driving is required the following day, an overnight stay at

destination may be advisable. Patients are advised to refrain

from driving if tired and sleepy.

Respiratory muscle and chest wall disorders

► HCT is recommended for all adult patients with FVC <1 L,

pending further data, and may be considered in others

thought to be at particular risk, including children with

reduced FVC due to respiratory muscle or chest wall

disorders.

► If patients are unable to perform spirometry reliably, a walk

test may be considered as an alternative.

► Patients should be advised to take daytime flights where

possible.

► Further planning and support are required for those estab-

lished on non- invasive ventilation (NIV) (see Appendix A).

(online supplemental appendix 2

Prevention of VTE during air travel

See table 1.

► Limit the risk of dehydration with adequate fluid intake.

► Avoid alcohol.

► Keep mobile, if possible, by walking around or doing seat-

based exercises once an hour.

► Consider graduated compression stockings (class 1 with

15–30 mm Hg).

► Low molecular weight heparin (LMWH) or a Direct Acting

Oral Anticoagulant (DOAC) are advised for both outward

and return long haul flights (long haul defined as flights

of 6–12 hours) in high- risk patients including those with a

history of VTE; local policy should be followed regarding

liaison with primary care and/or haematology services to

teach the patient how to administer the injection and dispose

safely of the equipment. There is no formally recommended

dose, but enoxaparin at a dose of 40 mg or weight based

1 mg/kg injected once 4–5 hours before the flight has been

suggested.

► The prophylactic doses of the DOAC may also be used.

► All patients with a recent (<6 weeks) history of VTE, espe-

cially any who presented with significant right ventricular

strain and decompensation should be reassessed before air

travel.

Air travel after VTE

► Air travel should be delayed for 2 weeks after a diagnosis of

DVT or pulmonary embolism (PE).

Pulmonary hypertension

► Those in New York Heart Association (NYHA) WHO

functional class 3 or 4 are usually advised to have in- flight

oxygen. If there is no evidence of hypercapnia it seems

reasonable to suggest 2 L/min by nasal cannulae. If there are

concerns about hypercapnia, HCT should be considered if

available.

► Those eligible for LTOT (sea level PaO

<8 kPa at rest on

air) should have in flight oxygen at double the flow rate

recommended at sea level, provided there is no evidence of

hypercapnia.

Table 1 Summary of risk factors for VTE during air travel

Risk status Risk factors Advice

All passengers Low Avoid excess alcohol and

caffeine- containing drinks

Remain mobile/exercise legs

Moderate risk Examples include:

Aged over 60

Extensive varicose veins

Recent minor surgery

Pregnancy

Above plus consider:

Take short periods of sleep

Support hosiery/graduated

compression stockings

High risk Examples include:

Previous VTE (and not on current

anticoagulation)

Thrombophilia

Within 6 weeks of major surgery

Current malignancy

If travel is essential, consider:

low- molecular- weight heparin

or formal anticoagulation

(including return journey)

This requires careful clinical

assessment

VTE, venous thromboembolism.

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BTS Clinical Statement

Lung cancer and mesothelioma

► Patients undergoing chemotherapy should not travel while

they are at increased risk of infection or suffering from

significant side effects, such as vomiting.

Hyperventilation and DB

► Patients with DB, inducible laryngeal obstruction (ILO) and/

or vocal cord dysfunction (VCD) should be referred to a

respiratory physiotherapy specialist for advice on symptom

management before travel.

► Those with anxiety disorders should be reviewed before

travel; compliance with medication assessed; and use of

short acting anxiolytics encouraged.

► Other life- threatening conditions presenting with dyspnoea

should be excluded on board as far as possible.

► Supplemental oxygen should be given on board if the cause

of breathlessness is unclear

► Rebreathing via a paper bag is not recommended.

HCT outcomes

Preﬂight respiratory screening

Why?

Medical incidents have been reported in around 1 in 600 flights,

or 1 in 30 000 passengers.

11 12

Estimates vary and reliable data

are difficult to obtain, but respiratory events account for around

12% of in- flight incidents. In a recent study of 1260 healthy

volunteers, no significant changes occurred in pulse oximetry

(SpO

) during a simulated 8- hour flight at cabin altitudes up to

2438 m (8000 ft).

However, if cabin altitude exceeds 3048 m

(10 000 ft), hypoxaemia becomes more prominent and SaO

falls to∼89% in healthy individuals.

Other potential hazards

for passengers with respiratory conditions include low rela-

tive humidity, and altitude- related expansion of gases within

enclosed pulmonary parenchymal spaces. It follows from Boyle’s

Law that a cabin altitude of 2438 m (8000 ft) will result in a 38%

expansion of humidified gas.

Who?

There is no good- quality evidence to determine who should have

a formal respiratory review before air travel. Experts generally

advise preassessment or screening for the following adults, chil-

dren and infants:

► Those with a respiratory condition with the potential to

deteriorate acutely resulting in incapacitation and/or the

need for medical intervention. This includes (but is not

exclusive to):

– Severe (FEV1 <50% predicted

or poorly controlled

obstructive airway disease (evidenced by symptoms, oxy-

gen requirements, severe and/or frequent exacerbations).

– Symptomatic restrictive lung or chest wall conditions, or

known respiratory muscle weakness causing breathless-

ness and exercise limitation.

– PH.

– Comorbid conditions which may be worsened by hypox-

aemia (cerebrovascular or cardiac disease).

– Recent (<6 weeks) hospital treatment for a respiratory

condition.

– Requirement for CPAP or ventilator support such as NIV.

– Active cancer with lung involvement.

– Patients requiring domiciliary oxygen.

► Recent (<6 weeks) pneumothorax and those at higher risk

of pneumothorax (cystic lung disease or recurrent pneumo-

thorax), and patients with trapped lung and a chronic air

space.

► Recent (<6 weeks) pulmonary embolus or deep venous

thrombosis, or increased risk of VTE.

► Anyone who has experienced significant symptoms during

previous air travel, or whose condition is of concern to their

physician.

The following are generally considered contraindications to

air travel:

► Untreated respiratory failure.

► Untreated pneumothorax.

► Active infection representing a risk to others for example,

TB, SARS, MERS, COVID- 19.

► Bronchogenic cysts. Cerebral air embolism, in some cases

fatal, has been reported in aircraft passengers after rupture

of a bronchogenic cyst.

► Patients with severe hypoxaemia requiring >4 L/min

in- flight oxygen were previously advised against air travel,

because 4 L/min was the maximum fixed flow rate routinely

available on commercial aircraft. With the availability of

flight approved POCs delivering a range of continuous

and intermittent flow rates, this cut- off no longer applies.

In- flight oxygen delivery is more varied, and maximum flow

rate is determined by the equipment available. Pulse- dose

delivery systems can however complicate determination of

the flow delivered and may not be well tolerated. The effects

of mouth- breathing, speech, snoring and/or sleeping should

be considered. High- flow nasal oxygen (HFNO) cannot be

delivered on board commercial aircraft.

In- flight oxygen may be contraindicated in adults and chil-

dren with a history of type 2 respiratory failure.

17 18

Hypoxic

challenge with arterial carbon dioxide tension (PaCO

) measure-

ment was advised for this group in 1996

but there has been

little research since. This document, therefore, follows the 2015

BTS Guideline for Home Oxygen Use in Adults

when making

recommendations for managing patients with previously docu-

mented hypercapnia.

Clinical practice points

► All patients should undergo careful initial evaluation with

history and physical examination by a clinician who is

competent. The history should include:

– Review of symptoms, baseline exercise capacity, recent

exacerbation history, treatments and previous experience

of air travel.

– Consideration of the logistics of the intended journey, to

include (if known):

– Number and duration of flights, including whether

daytime or overnight.

– Location of stop- over(s) and destination: these deter-

mine air quality, altitude and available medical facil-

ities.

– Time away from home.

– Return journey.

► Further assessment by a Respiratory Specialist is advised for

those in whom screening raises concerns, and hypoxic chal-

lenge testing may be advised.

Infants and children

In general, similar considerations apply to both adults and

children if they have severe chronic airway disease, or require

chronic supplementary oxygen, or non- invasive or tracheos-

tomy ventilation. Both children and adults with these condi-

tions require a preflight assessment. Similarly, unless otherwise

stated, recommendations for individuals with previous thoracic

surgery, pneumothorax or empyema apply to both adults and

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BTS Clinical Statement

children. There are, however, some specific considerations for

infants and younger children since several factors place infants

at greater risk of developing hypoxia. These factors include left

shift of the oxygen dissociation curve (due to the presence of

foetal haemoglobin), smaller airway diameter, relatively fewer

alveoli, compliant rib cage and increased tendency to pulmo-

nary vasoconstriction and bronchoconstriction and thus ventila-

tion–perfusion mismatch under hypoxic conditions. Moreover,

preterm infants and infants under 2 months of age may develop

apnoea/hypoventilation in response to hypoxia or infection.

20 21

Beyond 3 months of age there is no evidence that ex- preterm

infants, without bronchopulmonary dysplasia, are at significantly

greater risk of desaturation during a HCT than term infants.

In addition to very young and ex- preterm infants, the chil-

dren most at risk of hypoxia are those with anaemia, congenital

heart disease with an actual or potential right to left shunt,

neuromuscular disorders or chronic or acute lung disease. Low

humidity during air travel can also present a problem for chil-

dren with respiratory conditions such as CF. Those most at risk

of complications associated with reduced air pressure are chil-

dren with upper respiratory tract infections, or trapped intra-

thoracic air, including those with recent pneumothorax or cystic

lung disease.

For infants born at term (>37 weeks) it is prudent to delay

flying for 1 week after birth to ensure they are healthy.

In view

of their greater risk of apnoea and hypoxia, infants born prema-

turely (<37 weeks) with or without a history of respiratory

disease who have not reached their expected date of delivery

at the time of flying should have in- flight oxygen available.

HCT may not be a reliable guide of oxygen requirement in this

group.

If air travel is essential, they should travel with oxygen

at a tolerable low flow, recognising that this may be a minimum

of 1 L/min depending on equipment.

The following Clinical Practice Points are specific to infants

and children.

Clinical practice points

► For infants born at term (>37 weeks) it is prudent to delay

flying for 1 week after birth to ensure they are healthy.

► Infants born prematurely (<37 weeks) with or without a

history of respiratory disease who have not reached their

expected date of delivery at the time of flying should have

in- flight oxygen available. HCT may not be a reliable guide

of oxygen requirement in this group. If air travel is essen-

tial, they should travel with oxygen at a tolerable low flow

rate, recognising that this may be a minimum of 1 L/min

depending on equipment.

► Infants under 1 year with a history of chronic respiratory

problems should be discussed with a respiratory paediatri-

cian and HCT considered. Those with SpO

<85% on HCT

should have in- flight oxygen available; paediatrician discre-

tion should be used for infants with SpO

85%–90% recog-

nising that sleep or respiratory infection may further reduce

saturations in this group.

► In children with chronic lung disease able to perform

spirometry whose FEV

is consistently <50% predicted,

HCT should be considered. This includes children with CF

and PCD. Children with chronic lung disease who are too

young to perform spirometry reliably should have a clinical

assessment of disease severity and their likely tolerance of

hypoxia. In children with CF the disease is rarely severe

enough to compromise lung function significantly at this

age.

► Infants and children who have required long- term oxygen

in the last 6 months should be discussed with a respiratory

paediatrician and HCT considered.

How?

Pulse oximetry is the easiest and usually the first screening

test.

It has generally been accepted in the past that those with

resting SpO

>95% at sea level should not require in- flight

oxygen.

2 25 27–30

Spirometry results may already be available

in patients with known acute or chronic lung disease, or with

symptoms suggesting lung disease.

31 32

However, lung function

parameters are in many cases poor at predicting hypoxaemia or

complications.

28 33–35

Many airlines have historically considered that those able

to walk 50 m or climb up 10–12 steps without distress have

sufficient cardiopulmonary reserve to fly.

2 36

The role of the

6MWT in preflight evaluation, widely used to assess functional

capacity and exercise- induced hypoxaemia in COPD

37–40

and

ILD including IPF,

41–43

has also been examined. Current data

suggest that the 50 m walk test is an insensitive assessment of

‘fitness to fly’

38 44 45

although still sometimes referenced.

36 46 47

Several studies show no correlation between walking distance

and HCT outcome in patients with COPD, ILD or extrapul-

monary restriction.

38 44 45 48

One study showed no correla-

tion between exertional dyspnoea and HCT outcome.

The

50 m walk test alone thus appears unsuitable for preflight

assessment.

The 6MWT and externally paced incremental SWT may be

of value. Baseline values do not reliably predict in- flight hypox-

aemia in a number of respiratory conditions

1 4 33 34 44 49–51

but

changes in SpO

during 6MWT and SWT may correlate with

HCT outcome in COPD, ILD and chest wall deformity.

30 38 44 45

Walk tests cannot predict the in- flight oxygen flow rate required,

but they may help inform the decision as to who needs further

assessment.

A walk test is not always practical. Data from one small study in

COPD suggest that MRC scores may help predict the likelihood

of exercise desaturation.

From this it appears that patients with

COPD, MRC score 1 or 2 and resting oxygen saturations >95%

do not usually need further testing before air travel. If there

are still concerns, a walk test may help decide whether HCT is

required. In those with COPD who do undergo 6MWT or SWT

and do not desaturate below 84%, in flight oxygen should not be

required and they should not need HCT.

If resting oxygen saturations are SpO2 92%–95% and they

desaturate <84% but have no evidence of CO

retention, data

from Edvardsen et al

suggest it is reasonable to recommend

in- flight oxygen at 2 L/min without proceeding to HCT. Patients

in whom there are concerns about hypercapnia should proceed

to HCT.

Data are much more limited in restrictive disease, including

ILD, and baseline SpO2 does not appear to predict outcome.

In general, it seems reasonable to suggest that if baseline satu-

rations are >95% at rest and there is no desaturation below

95% on 6MWT or SWT, HCT should not be required. Those

with ILD and TLco ≤50% of predicted and PaO

≤9.42 kPa are

likely to need in- flight oxygen or HCT. If there are no concerns

about hypercapnia it may be reasonable to recommend 2 L/min

without recourse to HCT. If there are concerns about CO

reten-

tion, titration HCT will be required to determine the oxygen

flow rate.

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BTS Clinical Statement

Hypoxic challenge testing

HCT is performed using an inspired gas mixture containing

15% oxygen, which gives an approximate similar inspired

oxygen tension (PO

) to breathing air at the maximum allowable

cabin pressure altitude (2438 m or 8000 ft).

53 54

HCT is usually

performed in a specialist respiratory physiology unit. The provi-

sion of a 15% oxygen gas mixture can be achieved using one of

the methods described in online supplemental appendix B.

The closest approximation to aircraft cabin conditions entails

exposure to simulated altitude in a hypobaric chamber, but such

chambers are not available for clinical assessment. A reasonable

substitute is the normobaric HCT, described by Gong et al

in patients with chronic airflow obstruction. This assesses the

response to hypoxaemia achieved by breathing a hypoxic gas

mixture at sea level. Various methods of hypoxic gas delivery

produce equivalent results to tests in a hypobaric chamber or

during real flights in adults with COPD.

1 39 56–58

Data are limited

in other conditions as well as for children and neonates.

The HCT is used to help decide whether passengers with

respiratory disease need in- flight oxygen and at what flow rate.

It does not assess fitness for air travel, despite its reputation as

a ‘fitness to fly’ test. If healthcare providers give this impres-

sion in patient information, they must manage patient and carer

expectations accordingly. A ‘preflight oxygen test’ is a more

accurate description. Most patients do not require HCT as part

of preflight medical assessment, and there should not be pressure

on physicians to arrange, or healthcare professionals to perform,

unnecessary HCT.

The physiological response to hypobaric hypoxia

(PaO

<8 kPa) is increased ventilation.

Alterations in respi-

ratory pattern may adversely impact on lung mechanics,

which may be further impaired by gas expansion, reducing vital

capacity and increasing residual volume.

The increase in venti-

latory drive is likely to be limited on commercial flights,

but a

modest increase in ventilation can exhaust an already reduced

ventilatory reserve.

16 60 63

The usual consensus is to recommend in- flight oxygen if

PaO

is predicted to fall below 6.6 kPa (50 mm Hg) or SpO2

below 85% in flight. There is little high- quality evidence

supporting these cut- off values, but this PaO

value ensures

that SpO2 remains above the steep portion of the oxyhaemo-

globin dissociation curve.

Some authors consider 6.6 kPa

to represent the lower safe limit for hypoxaemia,

65 66

as PVR

increases sharply in response to arterial pO2 below this level,

with the potential for an acute increase in right ventricle after-

load and right ventricular dysfunction.

16 29

As many patients

with COPD have cardiac comorbidity,

hypoxaemia in these

patients could precipitate cardiac ischaemia; this is unlikely in

those with stable disease in NYHA functional class I or II (no or

mild limitation of physical activity).

In the absence of new

evidence to the contrary, the cut- off PaO

of 6.6 kPa during

HCT appears reasonable.

HCT outcomes do not predict respiratory symptoms during

air travel.

Such symptoms do not appear to result directly

from hypoxaemia,

but from a combination of poor respira-

tory mechanics and reduced respiratory reserve impairing the

response to hypoxaemia. Symptoms are more likely to occur in

those with more severe breathlessness at sea level.

4 72

Limited

evidence suggests that those who desaturate during HCT and

have previously experienced respiratory symptoms during air

travel can avoid these by using in- flight oxygen.

29 71

Symptoms

may also result from anxiety regarding air travel (see section on

hyperventilation and DB).

Patient selection for HCT

Those with stable respiratory disease without history of air travel

intolerance, normal resting and exercise SpO2 at sea level and

no significant cardiac comorbidity, are unlikely to need in- flight

oxygen and should not require HCT. Those who have had HCT

in the past should not need it repeated unless their clinical

condition has changed. The patient’s plans should, however, be

discussed with the patient’s respiratory physician, paediatrician

or specialist nurse.

Those already using LTOT will need in- flight oxygen. Ideally,

the flow rate required at cruising altitude should be determined

using HCT. If HCT is not readily available and there are no

concerns about hypercapnia, passengers already on LTOT should

be advised that they will need a flow rate 2 L/min greater than

their baseline flow rate. This should be sufficient to compen-

sate for the relative hypoxia at normal cabin altitude. However,

current POCs do not routinely offer continuous flow rates above

3 L/min, and a pulse- dose delivery mode at higher levels may not

always be suitable.

As noted above, it is not practical for all patients with COPD

who want to fly to undergo 6MWT. Respiratory physicians may

however wish to consider 6MWT if there has been a significant

change in the patient’s condition since the last assessment, or

in new patients previously unknown to the service. Those who

desaturate below 84% may then be referred for HCT at the

discretion of the respiratory physician.

Some data are available in smaller numbers of patients with

restrictive lung disease, but there is currently no consensus

regarding the best walk test or cut- off values. In a study of 14

patients with primary thoracic scoliosis, Bandyopadhyay et

al found that resting SpO2 >95% did not accurately identify

those who do not desaturate during HCT, and recommend a

low threshold for performing HCT on patients with thoracic

scoliosis.

Likewise, in a study of 13 patients with OHS, base-

line SpO2 did not predict HCT outcome.

In a study including

42 patients with ILD and 20 with extra- pulmonary restric-

tion

before and after ‘2 min of moderate exercise’, Ling et al

proposed that a postexercise SpO2 of no less than 95% could be

used to exclude the need for HCT. Further research is required

to determine the most appropriate assessments for patients with

a variety of restrictive lung diseases, including which (if any) can

reliably eliminate the need for HCT.

Clinical practice points: patient selection for HCT

See figures 1 and 2

The following patients should not require HCT

► Those with stable disease who have previously undergone

HCT (no recent hospital admissions, exacerbations, or

significant changes to treatment).

► Patients with COPD with baseline SpO2 ≥95% and either

MRC score 1–2 or desaturation to no less than 84% during

6MWT or SWT, should be able to travel without in- flight

oxygen.

► Those with previous significant intolerance to air travel,

such as mid- air emergency oxygen or diversion. These

should have in- flight oxygen available at 2 L/min provided

there is no history of hypercapnia.

► Preterm infants who have not reached their due date at the

time of travel, as testing is not a reliable guide of oxygen

requirement in these infants. These should have in-ﬂight

oxygen available, delivered at 1–2 L/min if they develop

tachypnoea, recession, or other signs of respiratory distress.

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BTS Clinical Statement

HCT should be considered for the following

► Patients with COPD with resting SpO

≤95%, MRC score 3

or greater, or desaturation to <84% on 6MWT or SWT, and

in whom there are concerns about hypercapnia

► Infants and children with a history of neonatal respiratory

problems, or existing severe chronic lung disease including

those with FEV1 persistently <50% predicted (see page 7).

► Adults and children with severe asthma, evidenced by

persistent symptoms and/or frequent exacerbations despite

optimal treatment (see BTS/SIGN Asthma Guideline

)

regardless of resting sea level SpO

► Patients with ILD in whom SpO

falls to <95% on exer-

cise, and whose resting sea level PaO

is ≤9.42 kPa or whose

TLCO is ≤50%.

► Those with severe respiratory muscle weakness or chest wall

deformity in whom FVC is <1 L.

► Those with existing or previous hypercapnia and those at

risk of hypercapnia, including those taking medication(s)

which can cause respiratory depression.

► Patients with a history of type 2 respiratory failure already

on LTOT at sea level. However, if there is no evidence of

hypercapnia, it seems reasonable to recommend an increase

in flow rate by 2 L/min in- flight, provided the equipment can

provide it (see Appendix A).

Clinical practice points: HCT results

► PaO

≥6.6 kPa (≥50 mm Hg) or SpO

≥85%: in- flight

oxygen not required.

► PaO

<6.6 kPa (<50 mm Hg) or SpO

<85%: in- flight

oxygen recommended.

► Where required, titrate oxygen to maintain PaO

≥6.6 kPa

or SpO

≥85% in adults, SpO

90% in children aged 1 year

or more.

Air travel may be contraindicated in infrequent cases when

supplementary oxygen, at the flow rate needed to maintain

PaO

≥6.6 kPa or SpO

≥85%, causes significant changes to pH

and pCO

. The 2015 BTS Guidelines for Home Oxygen Use in

Adults

consider that a pH <7.35, and a PaCO

increase >1 kPa

from baseline (within 20 min) is significant. Specialist respiratory

physicians should use their discretion to determine the risk in

individual cases and advise accordingly. Where hyperventilation

is suspected, especially in response to anxiety rather than hypox-

aemia, results should be interpreted with caution as there is a

risk of false negative results.

HCT methods

These are described in Appendix B.

Exertion on board

Studies in adults with COPD

33 77 78

or CF

have shown that

patients can develop profound hypoxaemia when exercising

under hypoxic conditions, whether on board a commer-

cial aircraft at cruising altitude or during HCT. This has been

reported in patients whose HCT results would otherwise not

warrant oxygen. In some cases, PaO

values as low as 3.9 kPa

have been recorded.

33 78

The combination of further hypoxaemia and increased venti-

latory demand from exertion while flying may challenge those

already approaching the limits of their respiratory reserve. It

therefore seems prudent to recommend that passengers with

significant respiratory limitation, regardless of whether they

travel with in- flight oxygen, should request an aisle seat near a

toilet to avoid long periods of walking.

1 29 80

Passengers should

keep active by undertaking seat- based exercises and/or standing

at intervals if flight conditions permit.

Patients who cannot tolerate withdrawal of supplemental

oxygen for even a short period of time should not travel by air,

as there will be periods of time when oxygen cannot be supplied.

POC use below 10 000 ft may in some circumstances be prohib-

ited by cabin crew. The reduction in cabin pressure between an

aircraft taking off and reaching 10 000 ft is small (10%) and

unlikely to have any clinical impact on those who do not usually

require oxygen at rest at sea level. Aircraft descent may however

take longer than ascent, and the time to landing may be less

predictable.

Disease/condition-speciﬁc advice

Chronic airﬂow obstruction including asthma and COPD

Most adults and children with well- controlled mild or moderate

airflow obstruction and no other co- morbidities should have no

problem with commercial air travel, but they should be prepared

for the possibility of an exacerbation of their condition. Air

travel presents a theoretical risk of bronchospasm because of

mucosal water loss due to low cabin humidity.

Cigarette smokers are at a physiological disadvantage during

exposure to altitude.

Every opportunity should be taken, when

reviewing travel plans, to take a smoking history and offer brief

intervention and smoking cessation referral as appropriate.

Asthma

While asthma is prevalent and has the potential to be life-

threatening, most episodes are not.

82 83

Most passengers with asthma will have relatively mild disease

and do not require HCT. HCT should however be considered

for those with severe asthma, regardless of baseline sea level

oxygen saturation. In a retrospective study of 37 adults with

severe asthma (as defined in the BTS/SIGN Asthma guide-

line

) undergoing HCT, two- thirds who fulfilled the criteria for

in- flight oxygen on HCT had baseline sea level oxygen satura-

tions of >95%.

The role of HCT has not been studied in children with severe

stable asthma. A study in 51 children aged 2–12 years requiring

transient oxygen therapy during an acute asthma attack

(SpO2 <92%) showed that although 5% failed HCT within 24

hours of discontinuing oxygen therapy, all passed the HCT when

retested at 48 hours.

Food allergy affects up to 8.5% of children and adults with

asthma,

and asthma is a risk factor for severe or fatal anaphy-

laxis.

Appropriate precautions for those affected include

wiping tray tables and hands, informing the airline beforehand

and the cabin crew of allergies, and not eating during flights or

bringing known ‘safe’ foods from home

Clinical practice points

► The patient’s condition should be optimised before travel,

with attention paid to inhaler technique and smoking cessa-

tion referral as required.

► All medications and spacer devices should be carried in hand

luggage to mitigate the risk of lost or missing hold baggage.

► Emergency medications, including salbutamol inhalers and

spacers, must be immediately accessible.

► Individuals prescribed epinephrine auto- injectors should

have them readily available.

► For acute exacerbations on board, the passenger’s own bron-

chodilator inhaler should be given, with a spacer if needed.

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BTS Clinical Statement

► The passenger should alert the cabin crew if symptoms do

not respond rapidly to use of the inhaler, or if they recur

after a short interval.

► If the passenger does not have their own inhaler with them,

or if it is inaccessible, the airline may carry an inhaler in the

emergency medical kit. Spacers are not commonly available.

► Those with severe asthma should consult their respiratory

specialist beforehand and consider taking an emergency

supply of oral corticosteroid in their hand luggage in addi-

tion to their usual medication.

► Passengers with severe asthma are advised to carry copies of

their asthma management plan and/or relevant clinic letters.

Information can be held securely as scanned copies on a

mobile phone, or on a digital platform such as the NHS App.

► Food allergy affects up to 8.5% of children and adults with

asthma and asthma is a risk factor for severe or fatal anaphy-

laxis. Appropriate precautions for those affected include

wiping tray tables and hands, informing the airline before-

hand and the cabin crew of allergies, and not eating during

flights or bringing known ‘safe’ foods from home.

Chronic obstructive pulmonary disease

Patients with COPD planning air travel need careful evaluation,

not only because of their respiratory disease, but also because of

their high levels of comorbidity.

71 89

Respiratory symptoms in those with COPD are common

during air travel, but Edvardsen et al have shown that HCT does

not predict respiratory symptoms during air travel in patients

with moderate to very severe COPD.

They suggest that exac-

erbation of comorbidities such as cardiovascular disease (the

most common cause of death in COPD) is the most threatening

consequence of severe hypoxaemia. This is consistent with data

showing a risk of cardiac arrhythmias and ischaemic chest pain

in patients with COPD unable to respond to the physiological

stressors of air travel.

55 70

Work by Robson et al shows that resting

sea level saturations alone do not predict HCT outcome.

Spirometry does not reliably predict hypoxaemia or compli-

cations in COPD.

It seems prudent to avoid air travel within 6

weeks of an exacerbation although there are few data to support

this recommendation. Patients with COPD are at greater risk

of VTE as a direct consequence of the underlying condition, as

well as after an exacerbation. They should be advised accord-

ingly, especially if planning longer flights when the risk is further

enhanced (see section on VTE).

90–92

See Figure 1.

Clinical practice points

► The patient’s condition should be optimised before travel,

with attention paid to inhaler technique and smoking cessa-

tion referral where appropriate.

► All medications and spacer devices should be carried in hand

luggage to mitigate the risk of missing hold baggage.

► Emergency medications, including salbutamol inhalers and

spacers, must be immediately accessible.

► For acute exacerbations on board, the passenger’s own

bronchodilator inhaler should be given, with a spacer if

appropriate.

► Passengers with severe COPD are advised to carry a copy of

their COPD management plan and/or relevant clinic letters.

This information can be held securely as scanned copies on

their mobile phone A history of previous pneumothorax or

bullous lung disease necessitates assessment by a respiratory

specialist to determine the potential risk of complications

from reduced cabin pressure.

► Patients with COPD are at greater risk of VTE as a direct

consequence of the underlying condition, as well as after an

exacerbation. They should be advised accordingly, especially

if planning longer flights when the risk is further enhanced.

► Patients requiring long- term oxygen therapy should also

plan for oxygen supplementation at their destination (see

online supplemental appendix 1).

► Wherever possible, those who have had a recent exacerba-

tion of their condition should not fly until their condition

is stable and use of reliever therapy has returned to their

usual baseline. If their condition deteriorates while overseas,

medical advice should be sought before undertaking the

return flight.

CF (adults and children)

The risks associated with air travel are greater for those with

CF than for healthy individuals.

This is despite the fact that

people with CF have been shown to tolerate PaO

values below

6.6 kPa (50 mm Hg) for several hours without cardiac decom-

pensation or cerebral symptoms

; do not usually have cardio-

vascular comorbidities; and are generally younger than patients

with other respiratory conditions. Hypoxaemia results mainly

from ventilation/perfusion mismatch attributable to chronic

inflammation and mucus plugging. It is not clear which physio-

logical values measured at sea level best predict hypoxaemia or

complications during flight.

In 1 study of 30 adults with CF undergoing HCT, four fulfilled

the study’s criteria for supplemental oxygen (PaO

<6.6 kPa) at rest

and a further 11 dropped below this threshold while walking slowly.

Variables obtained during CPET (including SpO

and PaO

) showed

a stronger correlation with arterial oxygen tension (Pao

) during

HCT than baseline SpO

or spirometry.

However, in children

with CF the sensitivity and specificity of preflight HCT have been

reported as 20% and 99% (using a cut- off of SpO

<90% during

HCT with FiO2 0.15), compared with 70% and 96% for spirom-

etry (cut- off FEV1 <50% predicted).

Combining spirometry

and HCT increased sensitivity to 80%. Spirometry may, therefore,

usefully predict who may desaturate during flight, and a cut- off of

FEV1 50% has been used to recommend HCT.

Passengers with CF should practise good hand hygiene using

soap and water or an alcohol- based hand gel, and avoid touching

their face, particularly after touching arm rests, food trays or

toilet doors to minimise risk of infection. These measures are

included within recommendations from the European Centres

of Reference Network for Cystic Fibrosis project, endorsed

by the European Cystic Fibrosis Society.

These also advise

checking the relevant airline policy and levels of CF healthcare

provision at the proposed destination before travel (see online

supplemental appendix 1).

Clinical practice points

► All medications and spacer devices should be carried in hand

luggage to mitigate the risk of missing hold baggage.

► Patients with CF under the age of 6 are likely to be well

enough to fly at the paediatrician’s discretion.

► In those with CF who are old enough for spirometry and

whose FEV1 is <50% predicted, HCT is recommended.

If SpO2 falls below the 90% cut- off, as outlined above,

in- flight oxygen is advised.

► In children with chronic lung disease able to perform

spirometry whose FEV

is consistently <50% predicted,

HCT should be considered. This includes children with

CF and non- CF bronchiectasis. Children with chronic lung

disease who are too young to reliably perform spirometry

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BTS Clinical Statement

should have a clinical assessment of assess disease severity

and their likely tolerance of hypoxia. For children with CF

disease is rarely severe enough to severely compromise lung

function at this age.

Non-CF bronchiectasis

Passengers with bronchiectasis should not necessarily be discour-

aged from flying, but air travel can pose challenges.

Clinical practice points

► Regular airway clearance is essential for those dealing with

overproduction of mucus.

► Advice from a respiratory physiotherapist on adapting

airway clearance techniques should be sought for long- haul

flights.

► Portable nebulisers and PEP devices may be considered, but

use of these devices in- flight must be approved by the airline

before travel.

Interstitial lung disease

Like individuals with airflow limitation, patients with ILD,

including pulmonary fibrosis, respond to hypoxaemia at

altitude with increased heart rate and minute ventilation.

In severe disease the ability to increase minute ventilation

is limited and the resulting hypoxaemia may be marked.

However, unlike COPD, where many patients appear to be

able to tolerate marked hypoxia,

patients with ILD may

have acute or subacute disease and be less able to withstand

marked hypoxia. There are fewer relevant studies available

in ILD, and patient numbers are smaller than in COPD

studies.

Two studies in patients with ILD (n=15 and 10, respectively)

have shown that sea level oxygen saturations do not reliably

predict HCT outcome, and that oxygen saturations fall signifi-

cantly after light exercise performed under conditions of normo-

baric hypoxia.

73 96

These findings are consistent with those from

the UK Flight Outcomes Study,

a prospective observational

study of 431 patients including 186 with ILD. This showed that

neither FEV1 nor sea level SpO

reliably predict desaturation at

altitude, and that patients with ILD were more likely than others

to require unscheduled healthcare for respiratory events within

4 weeks of air travel.

In a study including 15 patients with ILD, Martin et al found

that predictive equations overestimated the need for in- flight

oxygen in patients with ILD, as they did for those with COPD

and CF.

More recently, Barratt et al examined the predictive

value of various parameters for HCT outcome in 106 ILD

patients (69 with IPF).

Only the combined parameters

of TLCO >50% predicted and sea level PaO

>9.42 kPa

independently predicted a successful HCT outcome. From

analysis of a subset of 88 patients with a complete dataset

available the authors propose a new prelight algorithm for

patients with ILD with a sensitivity of 86% and specificity

of 84%. In patients with both sea level PaO

≤9.42 kPa and

TLCO ≤50% predicted, in- flight oxygen is recommended

without recourse to an initial diagnostic HCT. HCT for titra-

tion of the oxygen flow rate required on board is still advised.

For patients in whom either TLCO ≤50% or PaO

≤9.42 kPa,

diagnostic HCT is advised. This promising approach requires

further validation in a larger, prospective cohort of patients

with ILD, preferably supported by patient reported outcomes

from actual flight(s).

Clinical practice points

► In patients with comorbidity, including PH and/or cardiovas-

cular disease, attention should also be paid to the impact of

air travel on these conditions.

► Physicians may wish to consider HCT in those whom SpO2

falls to <95% on exercise, and/or in those in whom either

TLCO ≤50% or PaO

≤9.42 kPa (if available).

► Patients with TLco <50% of predicted or PaO

≤9.42 kPa

are likely to need in- flight oxygen. If there are no concerns

about hypercapnia it may be reasonable to recommend 2 L/

min without recourse to HCT. In those in whom there are

concerns about CO2 retention, titration HCT is advised to

determine the oxygen flow rate.

Thoracic surgery and other interventional procedures

There is no high- quality evidence in this area and further

research and/or data collection are needed. The following are

suggested time periods before which a medically unaccompanied

commercial flight can safely be undertaken after the specific

thoracic interventions described below. The advice is conserva-

tive. Shorter recovery periods may be appropriate in individual

cases, but only if approved by the doctor/surgeon carrying out

the procedure. It is also important to note that the potential

risks of travel are not just those associated with a postprocedure

pneumothorax, but include wound infection and pain, which

could require medical attention at destination and would need

approval by the travel insurer.

Thoracic surgery, including VATS procedures

In the absence of published evidence, we advocate a conserva-

tive and safe minimum time interval, with the caveat that flying

sooner after such procedures may be possible and/or desirable,

but that this should be agreed with the surgeon and discussed

with the airline. At least two UK centres independently advise

against non- essential air travel for 4 weeks after removal of

drains (Jon Naylor, personal communication). If air travel is

essential, a minimum delay of 2 weeks is advised, depending on

the type of surgery and the surgeon’s advice.

Clinical practice points

► The opinion of the surgeon or interventionalist should be

obtained before the patient travels by air. Patients, profes-

sionals, and their carers should be aware that this may result

in a delay of 4 weeks for non- essential air travel and 2 weeks

for essential air travel.

► Careful clinical assessment of the patient is required. This

should include consideration of their baseline status including

comorbidities, SpO2, postprocedure complications such as

infection and/or pain, flight duration and destination.

Percutaneous lung biopsy, pleural procedures (including

thoracocentesis, medical thoracoscopy and insertion of

indwelling pleural catheter)

A North American study of 179 patients, who between them

underwent 183 percutaneous transthoracic needle biopsies,

suggested that air travel was safe within 24 hours of procedure,

even in the 65 patients (35%) who developed a small, stable

postbiopsy pneumothorax.

Fifty (77%) of them flew within

4 days of the final postbiopsy chest radiograph. During a brief

telephone survey after the flight, 14 (8%) reported worsening of

pre- existing respiratory symptoms or new respiratory symptoms.

There were no reported events requiring in- flight medical atten-

tion or flight diversion. These were, however short, internal

North American flights over land, where diversion is relatively

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BTS Clinical Statement

straightforward if required. The situation for a UK- based patient

travelling on a long- haul flight to the Middle East, USA, Far East

or Australasia is quite different.

Clinical practice points

► The opinion of the interventionalist should be obtained

before the patient travels by air.

► Careful clinical assessment of the patient is required. This

should include consideration of baseline status including

comorbidities, SpO2, postprocedure complications such as

infection or pain, flight duration and destination.

► Patients with no pneumothorax seen on the postprocedure

chest X- ray should wait for 1 week before air travel.

► Patients with a pneumothorax seen on the postprocedure

chest X- ray should wait for 1 week after resolution on chest

X- ray before air travel.

‘Trapped lung’ after drainage of pleural space

Only very limited data are available, from a report of two patients

with a small chronic pneumothorax.

100

This suggests that such

patients may be able to travel safely by air, but require thor-

ough clinical assessment, CT imaging and HCT as a minimum

beforehand.

Clinical practice points

► The opinion of the interventionalist should be obtained

before the patient travels by air.

► Patients should be assessed carefully and advised on a case-

by- case basis.

► Patients should be clinically stable before air travel.

Bronchoscopic procedures

The risks associated with air travel are not only those of a

possible pneumothorax, but also the effects of sedation, exacer-

bation of pre- existing or new symptoms such as cough, hoarse

voice haemoptysis and dyspnoea, respiratory infection and the

consequences of arrhythmias observed during the procedure.

Clinical practice points

► The opinion of the interventionalist should be obtained

before the patient travels by air.

► Patients should be clinically stable before they travel.

► After interventional bronchoscopy including TBNA, TBB,

EBUS and endobronchial valve insertion, those with no

pneumothorax seen on the postprocedure chest X- ray

should wait for 1 week before air travel.

► After interventional bronchoscopy including TBNA, TBB

and EBUS, those with a pneumothorax seen on the post-

procedure chest X- ray should wait for 1 week after resolu-

tion on chest X- ray before air travel.

Pleural disease

Pleural effusion

Patients with stable pleural disease and normal resting oxygen

saturations should be able to fly without further precautions.

Those who have indwelling long- term drainage catheters should

be reminded that the manufacturers do not advise air travel.

Those who choose to travel should be encouraged to take a

supply of drainage bottles for their time away.

In those with a recent onset pleural effusion, investigation

should be delayed if air travel is planned within 2 weeks, since

intervention may increase the risk of pneumothorax. The risk of

delaying investigation should be discussed with the individual to

determine whether travel plans can be modified.

Pneumothorax

The prevalence of in- flight pneumothorax in passengers with

existing lung disease appears low overall, being zero in the

UK Flight Outcomes Study.

It increases, however, in those at

increased risk: 3.6% in a study of 276 patients with LAM

101

; and

9% within 1 month of air travel in a retrospective survey of 145

patients with BHD syndrome.

102

Most individuals with an untreated, closed pneumothorax

should not travel by air. In exceptional cases where the pneu-

mothorax is long- standing and thought to present a low risk,

secondary care evaluation is strongly advised before travel.

In individuals with a treated pneumothorax, exposure to alti-

tude poses a risk of recurrence. The 2010 BTS Pleural Disease

guidelines state that patients ‘…should be cautioned against

commercial flights … until full resolution of the pneumothorax

has been confirmed by a chest X- ray”.

103

These guidelines state

that patients should wait a week after pneumothorax resolution

before flying. There is limited, more recent evidence to suggest

that in the case of traumatic pneumothorax, air travel as early

as 72 hours after chest drain removal with full lung inflation

may be safe.

104

A prospective observational study of 20 patients

with a small residual traumatic pneumothorax, exposed to hypo-

baric hypoxia for 2 hours suggested no significant clinical effects

despite expansion of up to 171%.

105

The data should, however,

be interpreted with caution given the small numbers involved,

the small size of the pneumothorax in each case, and the limited

duration of hypobaric exposure. They are not sufficiently robust

to justify overriding current BTS guidance.

In those who have undergone thoracotomy and surgical

pleurodesis, the recurrence rate is so low that no subsequent

restriction on travel is necessary.

The recurrence rate has been

reported to be four times greater after video- assisted thoracos-

copy,

106

suggesting that this procedure may not be as definitive.

The risk of recurrence is greatest in those with pre- existing lung

disease, cigarette smokers and taller men.

Clinical practice points

► Passengers should not travel by air until 7 days after full reso-

lution on chest X- ray.

► Those at higher risk of recurrent pneumothorax should be

advised accordingly.

► Higher- risk groups, including those with cystic lung disease

such as LAM and BHD syndrome, should be advised

accordingly.

► Patients with trapped lung and a chronic air space thought

to present a low risk should be evaluated in secondary care

before travel.

Respiratory tract infections

Upper respiratory infection including otitis media and sinusitis

During air travel with acute infection of the upper airway, the

main risks are unpredictable, but may reflect previous experi-

ence. They are of pain and potential rupture of the tympanic

membrane. Those with significant symptomatic viral upper

respiratory tract infection may wish to delay travel because of

the risk of pain and disseminating infection to others.

Barotrauma, characterised by otalgia, is a consequence of

inability to equilibrate the pressure differential between the

external and middle ear. This is usually more severe during

landing than take- off. Most passengers, including older chil-

dren, can equilibrate the pressure through yawning, swallowing,

chewing or a Valsalva manoeuvre (eg, pinching the nose and

blowing). Infants and young children may be unable to perform

these manoeuvres, but swallowing may be encouraged by

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BTS Clinical Statement

drinking. It is also more frequent when the child is awake and/

or crying.

It has been estimated that 10% of adults and 22% of children

may have changes to the ear drum after a flight, although perfo-

ration is rare and symptoms usually resolve spontaneously.

107 108

Historically, oral (and to a lesser extent topical) decongestants

have been recommended for adults with risk factors for sinus or

middle ear barotrauma.

The evidence is very weak, and there

is no evidence in children. Treatment with intranasal steroids

(commenced at least a week before the flight) can however

improve symptoms, as for inflammatory rhinosinusitis. After an

episode of acute otitis media, patients are usually advised not to

fly for 2 weeks

107

Clinical practice points

► In passengers who develop sinus barotrauma after flying, it

may be helpful to consider topical and oral decongestants as

well as appropriate analgesia. Prolonged use of decongest-

ants is not advised owing to the risk of rebound congestion

on withdrawal.

► If there is an allergic component, intranasal steroids used

for a week prior to travel, and/or oral corticosteroids may

be considered.

► Symptoms and signs of barotrauma should have resolved

before flying again. This usually takes between 1 and 6 weeks.

► After an episode of acute otitis media, patients are usually

advised not to fly for 2 weeks.

Viral infections

Although viral infections may be transmitted on board, as in

any environment where people are in proximity for prolonged

periods, available data suggest this is not common on modern

commercial aircraft. This may reflect lack of face- to- face

contact, the barriers afforded by seat backs, and the characteris-

tics of cabin airflow on board, which is not front to back. Viruses

are within the particle size range captured by HEPA filters on

modern commercial aircraft, which are like those used in hospi-

tals. Transmission by droplet spread, including via fomites, is

applicable to all environments.

100 101

This may be reduced by

passengers wearing masks, frequent use of hand sanitiser and

disinfectant wipes for hard surfaces, and by regular deep cleaning

of the aircraft cabin. The risk of infection in airport facilities on

departure, during stopovers, and on arrival should also be consid-

ered. More general hygiene practices, such as handwashing and

covering the mouth and nose when coughing or sneezing, have

also been shown to reduce spread of viral infections.

109 110

Some respiratory viral infections may be more infectious than

others. A review of passengers on a flight carrying a confirmed

case of SARS in 2003 reported 16 cases of SARS developing in

fellow passengers,

111

but it seems likely that affected individuals

were in close proximity in the airport lounge, so transmission

may have occurred before boarding. To date there is just one

reported case of possible aircraft transmission of COVID- 19,

112

but the literature is clearly evolving.

The principal public health concern around air travel is the

role it plays in carrying infected persons (who may be asymp-

tomatic and are not always contagious) long distances within a

short space of time, with the associated risk of disseminating

novel contagious disease to new locations. This has been espe-

cially evident during the COVID- 19 pandemic. Special attention

should therefore be paid to the clearance of people wishing to fly

who have respiratory tract symptoms during outbreaks of such

infections. At any time, and not just during outbreaks of serious

infectious respiratory disease, airport screening measures may be

implemented and travellers with a fever can be refused boarding

by the airline. In cases of serious epidemics and/or pandemics

such as MERS and COVID- 19, even urgent travel may be

prohibited. The Centers for Disease Control and Prevention

website has regular updates on air travel (www.cdc.gov). The

2020 BTS COVID- 19 Statement on Air Travel contains prac-

tical advice for potential passengers with lung disease during the

COVID- 19 pandemic.

113

Clinical practice points

► Patients with highly contagious infections including measles,

chickenpox, mumps, SARS, MERS or COVID- 19 should not

be allowed to travel until they are considered non- infectious.

► Passengers should familiarise themselves with current

national and international regulations regarding air travel,

which should always be observed.

Tuberculosis

WHO provides comprehensive information about the risk of air

travel with TB.

114

Risk is determined by two factors: whether

acid fast bacilli are present on smears of respiratory samples, or

a sputum smear is culture positive; and whether drug resistance

is present. Patients with sputum smear or culture positivity are

considered potentially infectious.

Clinical practice points

► Smear positive patients must not fly until they have provided

two smear negative samples on treatment.

► Those starting treatment for pulmonary TB, where not all

the information is yet available, should not travel by air for

the first 2 weeks.

► For those who are smear negative and have a fully sensitive

organism, treatment would be expected to render them non-

infectious after 2 weeks.

► For patients with MDR/XDR TB, travel is prohibited until

two negative culture samples have been produced and there

is clinical evidence of improvement on treatment.

► Extrapulmonary TB does not usually warrant additional

precautions before air travel.

Pneumonia

Patients suffering from acute lobar bacterial pneumonia present

a low risk to other passengers. They are, however, more likely to

experience in- flight desaturation during flight.

Clinical practice points

► All but essential travel should be postponed for 7 days in

those who have reduced baseline sea level SpO2 (<94%).

OSAS and OHS

The most recent available guidance states that for patients with

OSAS, the potential risks during commercial airline travel are

worsening hypoxaemia when asleep, and exacerbation of jet lag

with potential adverse effects on driving.

Data are sparse regarding risks for passengers with OSAS

during air travel. Some data suggest there is a risk of cardiovas-

cular and other adverse events in this group when staying at high

altitude destinations. Hypobaric hypoxia can promote central

apnoeas in addition to obstructive events, which may cause

tachycardia, cardiac arrhythmia and systemic hypertension.

115

is not, however, clear how quickly this response develops, and

therefore whether the findings are relevant to air travel.

Using hypobaric chamber simulation testing, studies have

shown that there is an association between hypoxaemia,

decreased sleep time and an increased frequency of hypopneas

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BTS Clinical Statement

for patients with OSAS who are acutely exposed to high alti-

tude.

116

There are further adverse effects on sleep and OSAS if

alcohol

117

or sedatives

118

are taken.

Many patients with OSAS are already established on CPAP.

Some studies have shown that patients with OSAS have lower

oxygen saturations at baseline and at cabin altitude simulation

than normal subjects.

119

The changes are more marked in those

with severe OSAS. Use of CPAP at altitude is associated with

decreased central sleep apnoea and increased sleep efficiency.

116

Consideration must be given to the whole journey including

the return flight. This is especially important if the flight involves

an overnight element and patients expect to drive the next day.

Studies have identified that not using CPAP for one night during

the flight increases the risk of drowsiness at destination the

following day.

120

Careful planning is required. A retrospective survey of 394

patients who undertook air travel with CPAP reported that over

a third encountered problems with their equipment, power cord,

adapter or transport of the CPAP machine.

121

These findings

highlight the need for clinical teams to understand the logistics

so that they can support safe patient travel (see Appendix A).

In summary, the potential physiological risks for this group

include cardiac stress; increased frequency of hypopnoeas;

possible central apnoeas; hypoxaemia and exacerbation of jet

lag.

There are no data relating specifically to air travel in OHS,

which is considered a restrictive disorder. For these patients,

physicians should refer to guidance around the use of NIV in

those with respiratory muscle and chest wall disorders.

Clinical practice points

► Daytime flights are advised wherever possible.

► The patient should be advised to carry their CPAP device as

hand luggage, and a hospital letter to advise that the patient

uses CPAP.

► Careful planning and preparation are required, and use of

the patient’s own CPAP device is advised.

► Alcohol and sedatives should be avoided in the 12 hours

before, and during, airline travel.

► Patients should use their CPAP device on board if they are

travelling overnight, and avoid sleeping during daytime

flights.

► Consideration should be given to device settings and whether

adjustment is required for operation at altitude.

► Airline approval for carriage and use of device, including

battery specification, must be gained before travel.

► Consideration should be given to the whole journey. If

driving is required the following day, an overnight stay at

destination may be advisable. Patients are advised to refrain

from driving if tired and sleepy.

Respiratory muscle and chest wall disorders

There is little good evidence to guide decision- making around the

need for oxygen or NIV during air travel for patients with severe

extrapulmonary restriction resulting from chest wall disorder

or respiratory muscle weakness. One case report suggests that a

long- haul flight may have precipitated a first episode of PH and

right heart failure requiring intubation and ventilator support in

a man aged 59 with congenital kyphoscoliosis and apparently

stable cardiorespiratory function before travel. FVC was docu-

mented as 0.98 L on recovery.

122

Some work has been conducted to understand which patients

require HCT. The authors of a study of 21 adults with idiopathic

kyphoscoliosis or neuromuscular disease

123

concluded that

those with FVC <1 L, even with resting SpO2 >95%, are likely

to desaturate significantly at cabin altitude. In some restric-

tive conditions, for example, bulbar MND, FVC is difficult to

reproduce. Walk tests may aid decision- making in patients with

scoliosis,

but may also be inaccessible to those with MND and

similar conditions where spirometry is a challenge.

Since the 2011 BTS recommendations,

several studies have

tried to identify factors that may predict the need for in- flight

oxygen for patients with neuromuscular disease. One study

aimed to identify parameters that predict HCT outcome in 40

patients with MND. Baseline PaCO2 was the only independent

predictor of hypoxaemia during HCT.

124

This appears to be

supported by a more recent study examining baseline PaCO2

as a predictor of HCT outcome.

125

Patients likely to fail HCT

have a higher baseline PaC02, but the authors were unable to

determine an absolute threshold PaC02 value that could identify

patients needing in- flight supplementary oxygen.

Another study in 36 patients with MND examined baseline

lung function as a predictor of hypoxaemia in response to alti-

tude simulation.

126

The authors concluded that maximumin-

spiratory pressure (MIP) and sea level SpO2 may help identify

MND patients who will develop hypoxaemia at altitude. Despite

the small numbers, none of the patients with an MIP >30 mm

Hg or with sea level SpO2 >96% desaturated below 85% during

HCT. Preliminary data from a smaller study of 12 patients with

MND suggested that sniff nasal inspiratory pressure (SNIP) may

more accurately predict the risk of hypoxia during air travel

in those with neuromuscular disease and respiratory muscle

weakness.

127

While evidence to date addresses specific patient groups, the

principles may be applied to any individual with a restrictive

disorder resulting from respiratory muscle weakness or chest

wall deformity. Further research on the value of FVC, PaCO2,

MIP and/or SNIP in predicting HCT outcome in this group is

desirable. In the meantime, it seems reasonable to recommend

that individuals with severe respiratory muscle weakness or

chest wall deformity (FVC <1 L) should undergo HCT before

air travel. Physicians should use their discretion for considering

HCT if there are additional reasons for concern, such as a history

of previous travel intolerance, hypoxaemia or hypercapnia.

In those with respiratory muscle weakness, the possibility

of respiratory failure should also be considered. For patients

established on NIV, further planning and advice are required to

support the use of NIV during flight. If continuous flow oxygen

cannot be provided by the airline or by POC, oxygen and NIV

cannot be used simultaneously. A decision around whether NIV

or supplementary oxygen is of greatest physiological impor-

tance to the patient is then required on an individual basis. The

previous travel history, current clinical condition and the pres-

ence or absence of overnight travel should also be considered.

(see Appendix B, table 2).

In summary, the potential physiological risk for patients with

restrictive respiratory disease is respiratory failure resulting

from inadequate ventilation. It is therefore essential to assess

ventilatory requirements before deciding whether supplemen-

tary oxygen is required. The risk of respiratory failure must be

understood and assessed before travel, and there are currently no

absolute predictors to guide which patients are likely to require

supplementary oxygen.

Clinical practice points

► HCT is recommended for all adult patients with FVC <1 L,

pending further data, and may be considered in others

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BTS Clinical Statement

thought to be at particular risk, including children with

reduced FVC due to respiratory muscle or chest wall

disorders.

► If patients are unable to perform spirometry reliably, a walk

test may be considered as an alternative.

► Patients should be advised to take daytime flights where

possible.

► Further planning and support are required for those estab-

lished on NIV (see Appendix A).

VTE (DVT and PE)

Prevention of VTE during air travel

The risk of VTE during air travel appears low overall, and

prophylaxis is unnecessary for most travellers. Prolonged travel

(exceeding 6 hours) and/or the coexistence of another risk factor

for VTE increase the risk. The incidence of symptomatic VTE

has been estimated at 0.5% on flights over 12 hours, but asymp-

tomatic rates may be higher.

128–130

The reasons for the increased

risk are not entirely clear. Potential contributory factors include

prolonged immobility and dehydration, but these are not conclu-

sively proven. Other risk factors for VTE such as obesity, recent

surgery, pregnancy, malignancy and previous VTE all increase

the overall risk for travel- related VTE and may necessitate addi-

tional prophylaxis.

General measures, including getting up and walking around

where possible every 2–3 hours; ankle and calf exercises and

avoidance of alcohol or sedating drugs; are advisable for most

travellers. Although there is no conclusive evidence that flying

causes dehydration, the fall in cabin humidity along with alcohol

consumption and reduced fluid intake, may increase the risk on

long haul flights. Remaining well hydrated is, therefore, advis-

able. Wearing graduated compression stockings during travel

may reduce the incidence of deep venous thrombosis.

131

Data

are sparse regarding the method or duration of pharmacolog-

ical prophylaxis, and recommendations rely on consensus expert

opinion. Physicians may wish to recommend pharmacological

prophylaxis for those at higher risk of VTE, for example an

obese patient planning a flight exceeding 6 hours with a history

of recent surgery. The risks of prophylaxis are thought to be low.

There is limited evidence for LMWH as prophylaxis.

132

There is

no formally recommended dose, but enoxaparin 40 mg at a dose

of 40 mg or weight based 1 mg/kg injected once 4–5 hours before

the flight has been suggested.

132

The use of factor Xa inhibitors

is off- licence in this situation and currently has no evidence base.

Clinical practice points

► Limit the risk of dehydration with adequate fluid intake.

► Avoid alcohol.

► Keep mobile, if possible, by walking around or doing seat-

based exercises once an hour.

► Consider graduated compression stockings (class 1 with

15–30 mm Hg).

► LMWH or a DOAC are advised for both outward and return

long haul flights (long haul defined as flights of 6–12 hours)

in high- risk patients including those with a history of VTE;

local policy should be followed regarding liaison with

primary care and/or haematology services to teach the

patient how to administer the injection and dispose safely

of the equipment. There is no formally recommended dose,

but enoxaparin at a dose of 40 mg or weight based 1 mg/kg

injected once 4–5 hours before the flight has been suggested.

► The prophylactic doses of the DOAC may also be used.

► All patients with a recent (<6 weeks) history of VTE, espe-

cially any who presented with significant right ventricular

strain and decompensation should be reassessed before air

travel.

Air travel after VTE

Although the risks of prolonged air travel and development of

VTE are well known, there are fewer data on the risks associated

with flying after a diagnosis of VTE.

A patient with a confirmed diagnosis of PE is highly likely to

start anticoagulation, with the aim of preventing the formation

of new deep venous thrombi and further PEs. There is a general

acceptance that flying immediately after a diagnosis of PE/DVT

should be avoided. It appears reasonable to assume that the

sooner air travel occurs after a PE the greater the likelihood that

hypoxic pulmonary vasoconstriction will exacerbate ventilation-

perfusion mismatch and raise pulmonary pressures, affecting

cardiac output.

Some authors, but not all, suggest that most clots are resolved

after 14–21 days.

133

Consensus opinion is to delay air travel,

if possible, usually for at least 2 weeks, although there are no

concrete data to support a safe time interval. Clearly the risk-

benefit ratio needs to be assessed if more urgent air travel is

needed. Clot resolution depends principally on in vivo fibrino-

lysis. Consideration should be given to the severity of the initial

presentation. It is good practice, before any proposed air travel,

to reassess clinically a patient who has presented with significant

right ventricular strain and decompensation.

The probability of recurrent VTE while anticoagulated is

extremely low. Recovered, stable patients who remain on antico-

agulation should be reassured accordingly and advised to follow

the above general measures.

Clinical practice point

► Air travel should be delayed for 2 weeks after a diagnosis of

DVT or PE.

Pulmonary hypertension

Data are sparse, and recommendations are largely based on

expert consensus opinion. The concern in PH is the risk of

hypoxia causing increased pulmonary arterial pressure and right

ventricular strain. Most studies have employed HCT. They have

shown that most patients with PH can tolerate this degree of

hypoxia with minor increases in dyspnoea.

134

Furthermore, the

effect on the right ventricle in one study has been shown to be

minimal.

134

However, most of these studies only covered a short

Table 2 Clinical practice points: Hypoxic challenge test (HCT)

outcomes

PaO

≥ 6.6 kPa (≥ 50 mm Hg);

SpO

≥ 85%

In- ﬂight oxygen not required

PaO

< 6.6 kPa (<50 mm Hg);

SpO

<85%

Repeat HCT with oxygen (ﬂow rate and modality

ideally the same as that to be given on board

aircraft):

► Titrate oxygen to maintain PaO

≥ 6.6 kPa or

SpO

≥ 85%

► Monitor pH and pCO

if there is a history of

hypercapnia

Consider advising against air travel if pH falls to

<7.35 and PCO

increases by > 1 kPa (7.5 mm Hg)

from baseline when PaO

is maintained at ≥ 6.6

kPa or SpO

≥85%

The use of arterial or capillary blood gas sampling is preferred if available. Blood

gases are not routinely measured in children.

Recommendations on pCO

and pH changes are based on the 2015 BTS guideline

for home oxygen use in adults.

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BTS Clinical Statement

time period.

134

Longer exposure to hypoxia on long haul flights

may have more significant effects.

One study has monitored patients during commercial

flights.

135

This showed that up to a quarter of patients with

PH desaturate during short haul flights, with higher altitude,

ambulation and longer flights correlating with desaturations.

Most tolerated this well, with fewer than 40% of participants

reporting symptoms. A larger questionnaire based retrospective

study has also confirmed that in most patients with stable PAH,

flight is well tolerated with minimal clinical effects.

136

Around

half those surveyed travelled with supplementary oxygen.

Hypoxia reduces exercise capability; breathing oxygen-

enriched air improves exercise capacity.

134

It therefore appears

logical to give patients with impaired functional capacity supple-

mental oxygen on board the aircraft. Whether patients should

have oxygen while walking around as well as when sitting is

unknown; ambulatory oxygen on board presents obvious logis-

tical challenges.

The 2011 BTS Recommendations advised that patients in

NYHA WHO functional class 3 or 4 should have supplemental

oxygen during air travel.

This recommendation is pragmatic

rather than evidence based; and may result in over- prescribing

of in- flight oxygen. One study suggests that more than double

the number of patients would be recommended in- flight oxygen

based on functional class rather than HCT outcome.

134

If HCT is not readily available and there are no concerns about

hypercapnia, passengers already on LTOT should be advised that

they will need a flow rate 2 L/min greater than their baseline

flow rate. This should be sufficient to compensate for the rela-

tive hypoxia at normal cabin altitude.

Clinical practice points

► Those in NYHA WHO functional class 3 or 4 are usually

advised to have in- flight oxygen. If there is no evidence of

hypercapnia it seems reasonable to suggest 2 L/min by nasal

cannulae. If there are concerns about hypercapnia, HCT

should be considered if available.

► Those eligible for LTOT (sea level PaO

<8 kPa at rest on

air) should have in flight oxygen at double the flow rate

recommended at sea level, provided there is no evidence of

hypercapnia.

Lung cancer and mesothelioma

When evaluating those with lung cancer or mesothelioma it is

important to consider the nature and extent of their condition as

well as their treatment. A pragmatic approach is to evaluate their

risk of haemorrhage, pneumothorax, pleural effusion, VTE and

any recent surgical and/or bronchoscopic interventions.

If taking medication, and particularly controlled drugs,

patients must be aware of the appropriate documentation

required for the countries they are visiting. Advance- planning

is essential.

Clinical practice point

► Patients undergoing chemotherapy should not travel while

they are at increased risk of infection or suffering from

significant side effects, such as vomiting.

Hyperventilation and DB

There are few data on the implications of functional breathing

disorders for air travel, whether DB, VCD or ILO. Asthma should

not be overlooked as a possible association in those with DB.

137

Acute shortness of breath is one of several symptoms for which

flight diversion is advised.

138

Diversions are costly, typically

ranging from £10 000–£80 000 depending on aircraft size and

diversion destination.

139

Dyspnoea caused by DB or hyperven-

tilation is unlikely to have serious clinical consequences; but

it must be distinguished from dyspnoea attributable to life-

threatening acute medical conditions such as acute coronary

syndrome or PE.

1 140

Data from the last two decades suggest that 65% of in- flight

medical emergencies were due to exacerbations of pre- existing

conditions and that respiratory problems were most common;

half were due to asthma or ‘asthma- like’ presentations.

141–143

Air travel can be stressful. Physiological or psychological stress

may precipitate acute breathlessness in patients with respiratory

disease.

144

Acute hyperventilation can be a response to stress

independent of lung pathology, usually in those with known

panic and anxiety disorders.

145

Hyperventilation can cause bronchoconstriction resulting in

‘asthma- like’ symptoms

146

which are unresponsive to standard

asthma medication.

147 148

A perception that the usual ‘rescue’

medication is ‘not working’ may worsen an individual’s breathing

pattern, causing concern to them, other passengers and air crew.

Similar situations can arise with ILO or VCD, and onset of symp-

toms is often sudden.

149

Where DB is linked to respiratory conditions, particularly

asthma, national and international guidelines endorse breathing

exercise programmes provided by a specialist respiratory physio-

therapist as an adjuvant to pharmacological treatment. Patients

should be advised to use breathing techniques in situations where

breathlessness may become problematic.

75 150

ILO and VCD,

which can present with acute respiratory distress and stridor,

may be treated with breathing exercises taught by a respiratory

physiotherapist or a speech therapist with specialist expertise in

paradoxical vocal cord movement.

151

Paper bag rebreathing is no longer recommended, because

inspired oxygen concentration decreases sufficiently to endanger

hypoxic patients. There are data reinforcing that significant

harm to patients can result from acute myocardial infarction,

pneumothorax and PE being misdiagnosed as hyperventilation.

152

153

Clinical practice points

► Patients with DB, ILO and/or VCD should be referred to a

Respiratory Physiotherapy Specialist for advice on symptom

management before travel.

► Those with anxiety disorders should be reviewed before

travel; compliance with medication assessed; and use of

short acting anxiolytics encouraged.

► Other life- threatening conditions presenting with dyspnoea

should be excluded on board as far as possible.

► Supplemental oxygen should be given on board if the cause

of breathlessness is unclear.

► Rebreathing via a paper bag is not recommended.

Appendix A Logistics of air travel with equipment

Oxygen

Passengers requiring oxygen and travelling overseas will usually

need to lease a POC privately, since UK companies do not gener-

ally allow equipment provided through the NHS to be taken

out of the country. Furthermore, most airlines have moved away

from supplying routine medical oxygen.

Where battery powered mechanical devices are required

in- flight, including a POC, sufficient batteries should be carried

for 1.5 times the anticipated duration of the journey to cope

with delays or diversions. For example, a patient using a POC

on a 4- hour flight should have 6 hours of battery life. Any spare

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BTS Clinical Statement

batteries must be correctly packaged and should be carried in

cabin baggage. The airline must be notified in advance of these

plans, or airline staff can refuse to allow the equipment to be

taken on board.

Pulse- dose oxygen may not be suitable for patients with a fast

and shallow respiratory pattern, or during sleep.

154 155

Pulse-

dose settings do not equate to the equivalent continuous flow

rates,

and not every POC functions well at altitude.

156

contrast, pulse- dose oxygen functions reliably when provided

by a cylinder and conserving device.

156

One author found

significantly lower PaO

values when using a POC, compared

with compressed oxygen with a conserving device. Acceptable

in- flight values are achievable with POCs, but the dose may need

to be increased.

Pulse- dose delivery systems can complicate determination of

the flow delivered; and may not be well tolerated. The effects

of mouth- breathing, speech, snoring and/or sleeping should be

considered. HFNO cannot be delivered on board commercial

aircraft.

Pulse- dose oxygen has not been studied in infants and chil-

dren; and should not be used unless they have been shown to

trigger the device’s inspiratory flow.

Currently available POCs that do supply continuous flow

oxygen cannot provide flow rates above 3 L/min. Passengers

must refer to POC documentation to check that the equipment

meets their requirements before they lease it for air travel.

For all these reasons, assessments would ideally take place

using the same equipment as that which will be used on board

the aircraft. This is only likely to be possible when the patient

has leased or purchased a POC for their own long term, private

use.

Continuous positive airway pressure

Few airlines, if any, allow any medical device to be powered via

the aircraft power supply. An appropriate battery must, there-

fore, be used. The device and battery specifications must be

approved for use by the airline before travel. Battery perfor-

mance should be checked by the user beforehand, so there is an

understanding of operating times on their usual settings.

Further consideration needs to be given to CPAP use during

flight and at high altitude destinations, as it requires a machine

that will perform adequately at low ambient pressure. The 2011

BTS guidance

reported that a fixed- pressure CPAP machine

without pressure compensation, set to deliver a pressure of

12 cm H

O at sea level, may deliver only 9 cm H

O at 8000

ft. The machine may therefore require adjustment to ensure a

safe level of treatment throughout the flight. If continuous flow

oxygen cannot be provided by the airline or by POC, oxygen and

CPAP cannot be used simultaneously. The availability of distilled

water for humidifiers may be restricted.

Non-invasive ventilation

For patients established on NIV, further planning and advice

are required to support the use of NIV during flight. If contin-

uous flow oxygen cannot be provided by the airline or by POC,

oxygen and NIV cannot be used simultaneously. A decision

around whether NIV or supplementary oxygen is of greatest

physiological importance to the patient is then required on an

individual basis. Previous travel history, current clinical condi-

tion and the presence or absence of overnight travel should also

be considered. The level of clinical and personal dependency

must be considered in the context of requirements for trained

supervision and assistance by the caregiver.

Appendix B Quick reference guide for respiratory

physiologists

Most patients with respiratory conditions are able to fly safely

without any additional support. The following guide provides

specific information for respiratory physiologists regarding

patients who do need further investigation before embarking on

air travel. See figure 3.

HCT methods

The HCT uses an inspired gas mixture containing 15% oxygen,

which gives an approximate similar PO

to breathing air at

the maximum allowable cabin pressure altitude (2438 m or

8000ft).

53 54

HCT is usually performed in a specialist respiratory

physiology unit. The provision of a 15% oxygen gas mixture can

be achieved as follows:

► A premixed cylinder containing a 15% oxygen gas mixture

can be obtained from medical gas providers, or Douglas bags

can be mixed with air and nitrogen to reduce the percentage

of inspired oxygen to 15%, both to supply a tight- fitting face

mask in a closed circuit.

► Pure nitrogen can be introduced into a sealed chamber such

as a body plethysmograph for paediatric or mask- intolerant

patients, removing the need for a face mask.

Paediatric

patients can be sat in a body plethysmograph on an adult’s

lap throughout;

the adult should also undergo SpO

moni-

toring to avoid excessive hypoxaemia. A body box is gener-

ally used for children, although some paediatric laboratories

use masks

► A 40% Venturi oxygen mask can be used with pure nitrogen

as the driving gas, giving a resultant gas mixture containing

approximately 15% oxygen.

11 58

► A hypoxic gas generator, like an oxygen concentrator, can

be used to provide a continuous supply of variable hypoxic

gas mixtures to supply a mask or closed chamber. This can

be the most cost- effective method for centres with a high

demand for HCT.

The patient usually breathes the hypoxic gas mixture for

20 min, or until SpO

reaches 85%. Although this is shorter

than the briefest commercial flight, oxygenation equilibrium is

usually reached within this time.

134 157

The patient is advised to

have in- flight oxygen if PaO

falls below 6.6 kPa (<50 mm Hg)

or SpO

remains <85%

1 17

(see page 11).

HCT with oxygen

If PaO

or SpO

values meet the criteria, in- flight oxygen is

recommended.

The flow rate required can be assessed as part

of the HCT.

Previous BTS recommendations advised in- flight

oxygen to be supplied at two or 4 L/min via nasal cannulae,

which were for many years the only fixed flow rates routinely

available on commercial aircraft. As airline- supplied in- flight

oxygen becomes less common and greater numbers of patients

travel with flight- approved POCs delivering a wide range of

continuous and intermittent flow rates, these figures are less crit-

ical. The HCT should ideally be performed with the modality

that is intended for use in- flight.

Most airlines have moved away from supplying routine medical

oxygen. In- flight oxygen is thus now likely to be supplied by

an FAA approved POC, leased by the patient. These are mostly

pulse- dose delivery. It is, therefore, advisable to conduct a titrated

HCT with pulsed dose oxygen to maintain PaO

at ≥6.6 kPa or

SpO2 ≥85%, using setting 2 as the starting point. This approx-

imates to the 2 L/min originally stated. If pulse- dose oxygen at

higher settings is insufficient to maintain PaO

at ≥6.6 kPa or

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BTS Clinical Statement

SpO2 ≥85%, then continuous oxygen should be considered. It

should be noted that POC models supplying continuous flow are

limited, and they do not currently supply >3 L/min.

Pulse- dose delivery is not suitable for young children, for use

during sleep

154 155

or for certain adults. Not all POCs function

as expected under conditions of simulated altitude

156

and pulse-

dose settings may not equate to equivalent continuous flow rates

(see Appendix A).

Patients with hypercapnia

Previous BTS advice was to err on the side of recommending

oxygen if in doubt,

and other authors have recommended

doubling oxygen flow rates for patients with a pre- existing

oxygen requirement.

1 29

However, there is a potential risk of

developing hypercapnia and respiratory acidosis from oxygen

during HCT in patients with type 2 respiratory failure.

Patients

with a history of hypercapnia should ideally undergo HCT with

blood gas sampling. In these cases, the minimum amount of

oxygen should be delivered to maintain PaO

≥6.6 kPa while

monitoring PaCO

and pH. If blood gas sampling is not available

then care should be taken not to raise SpO

above the resting

level with supplementary oxygen in this group of patients .

some cases it may be unsafe to undertake air travel even if good

oxygenation can be achieved, if adverse PCO

and pH changes

are evident.

Figure 3 HCT for physiologists.

19CokerRK, etal. Thorax 2022;0:1–22. doi:10.1136/thoraxjnl-2021-218110

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BTS Clinical Statement

An incidental finding of an elevated COHb during HCT

represents an important opportunity to take a smoking history

and offer smoking cessation referral as appropriate.

Twitter Robina Kate Coker @RobinaCoker1

Acknowledgements The assistance of the British Thoracic Society Standards of

Care Committee is gratefully acknowledged. The Society and the Air Travel Clinical

Statement Group is also grateful to the organisations that provided feedback as part

of the consultation process.

Contributors RKC was the lead author responsible for the ﬁnal document. All

authors agreed the outline and content of the document and authored sections of

the document.

Funding The authors have not declared a speciﬁc grant for this research from any

funding agency in the public, commercial or not- for- proﬁt sectors.

Disclaimer A Clinical Statement reﬂects the expert views of a group of

specialists who are well versed in the topic concerned, and who carefully

examine the available evidence in relation to their own clinical practice. A Clinical

Statement does not involve a formal evidence review and is not developed in

accordance with clinical practice guideline methodology. Clinical Statements

are not intended as legal documents or a primary source of detailed technical

information. Readers are encouraged to consider the information presented and

reach their own conclusions.

Competing interests AA declared funding from Fisher Paykel and Breas. CC

declared funding from Pﬁzer, GSK, Janssen, MSD. SH declared funding from Astra

Zeneca, GSK, Roche, Chiesi, Trudell, Boehringer Ingelheim, Mylan, Teva.

Patient consent for publication Not applicable.

Provenance and peer review Not commissioned; externally peer reviewed.

Open access This is an open access article distributed in accordance with the

Creative Commons Attribution Non Commercial (CC BY- NC 4.0) license, which

permits others to distribute, remix, adapt, build upon this work non- commercially,

and license their derivative works on different terms, provided the original work is

properly cited, appropriate credit is given, any changes made indicated, and the use

is non- commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

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