AIR TRAVEL FOR PATIENTS-PRECAUTIONS

Flying with Medical Conditions

Over one billion people travel by air each year.The information in this article refers to considerations regarding fitness to fly as a passenger.

The information given is general and not exhaustive; the links to the individual guidelines should be used to examine issues in more detail. Individual patients may need to have several conditions taken into account and different airlines have varied policies. More difficult cases are best considered with specialist advice and/or liaison with the particular airline's medical advisors. The sources of advice used are only guidelines and clinical judgement should always be used in their interpretation.

Some airlines require medical certificates confirming that a patient is currently stable and fit to fly. Most have medical advisors who provide advice and 'clear' passengers as fit to fly.They may ask for a medical information form (MEDIF). The  Medical Association's advises doctors 'to word statements on a person's fitness to fly carefully, indicating the information on which the advice is based, rather than positively certifying a person's fitness'. For example:

• 'I know of no obvious reason why this person should not fly'; OR
• 'There is nothing in the medical record to indicate that flying is risky for this patient'.

This ensures that the doctor is not guaranteeing in any way that this patient can travel without any problem but rather saying that, on the available evidence, there is nothing to indicate a greater risk for this person than for others. However, the doctor is partly dependent on what the patient chooses to disclose to them about past health problems.

The main factors to take into account are whether air travel could adversely affect a pre-existing medical condition and whether or not a patient's condition could adversely affect the comfort and safety of the other passengers, or the operation of the flight. Regardless of a doctor's opinion on this latter question, the ultimate sanction to refuse travel lies with the airline and captain of the flight. If they consider there is a risk to the aircraft or its passengers, they may refuse to carry a particular passenger.

Physiology during flight

Modern aircraft are not pressurised to sea level equivalent. Cabin altitude equivalent is usually between 5,000 and 8,000 feet which means that there is a reduction in barometric pressure and a reduction in the partial pressure of alveolar oxygen (P_aO₂). Sometimes during flight, although not usually for long periods, oxygen saturation levels can fall to around 90%. A healthy individual can usually tolerate this with no problems but it may not be the same for someone with cardiac or respiratory conditions or with anaemia.

Aircraft cabins also have low humidity levels which can cause dryness of mucous membranes and also the skin. Reduced cabin pressure can also cause gas volume expansion. This can be a problem if there has been recent surgery that has introduced gas into the abdominal cavity or the eye. Gas can also expand if it has been trapped in the ear.

Basic considerations

Basic considerations when assessing a patient's fitness-to-fly include:

• The effect of mild hypoxia and decreased air pressure in the cabin.
• The effect of immobility.
• The ability to adopt the brace position in emergency landing.
• The timing of regular medication for long-haul/transmeridian travel.
• The ability of the patient to cope mentally and physically with travel to and through the airport to reach the flight and on disembarkation.
• Will the patient's medical condition adversely affect the comfort or safety of the other passengers and the operation of the aircraft?
• What health insurance cover does the patient have in case of problems?

Cardiovascular disease

Cardiovascular contra-indications to commercial airline flight include:

• Uncomplicated myocardial infarction (MI) within 7 days (exercise testing to show that there is no residual ischaemia or symptoms is not mandatory before travel).
• Complicated MI within 4-6 weeks.
• Unstable angina.
• Decompensated congestive cardiac failure.
• Uncontrolled hypertension.
• Coronary artery bypass graft within 10 days.
• Cerebrovascular accident within 10 days (some can travel after 3 days if assessed and stable).
• Uncontrolled cardiac arrhythmia.
• Severe symptomatic valvular heart disease.
• Uncomplicated percutaneous coronary interventions (e.g. angioplasty with stent placement) within 5 days - individual assessment is needed after that to ensure fitness and stability.

The decrease in oxygen saturated during air travel may affect those with cardiovascular disease. Indications for in-flight oxygen in cardiovascular disease include:

• Need for oxygen at baseline altitude.
• Heart failure -  Class III-IV or baseline PaO₂ <70 mm Hg
• Angina Class III-IV.
• Cyanotic congenital heart disease.
• Primary pulmonary hypertension.
• Other cardiovascular diseases associated with known baseline hypoxia.

It is unusual for patients to be allowed to take their own oxygen supply and oxygen is usually arranged by the airline who must be aware in advance. A fee is usually charged. This may change in the future and there are ongoing discussions regarding this.

Patients with pacemakers and implantable cardioverter defibrillators can fly once medically stable.

Deep vein thrombosis

• The World Health Organization (WHO) published the results of phase I of their WRIGHT (= WHO research into global hazards of travel) project in 2007.
• These results show that the risk of venous thromboembolism (VTE) approximately doubles after a long-haul flight (>4 hours).The risk increases with the duration of the travel and with multiple flights within a short period.
• It is immobilisation rather than any cabin environment effects of the coagulation system that is thought to be the cause of the increased risk.
• The risk also increases significantly in the presence of other known risk factors for VTE (obesity, extremes of height, use of oral contraceptives and the presence of prothrombotic blood abnormalities).
• The absolute risk of VTE per flight longer than 4 hours in a cohort of healthy individuals was 1 in 6,000.
• Effective preventative measures will comprise phase II of the WRIGHT project.

Deep vein thrombosis (DVT) prophylaxis

It is wise for anyone undertaking a long-haul flight to take sensible precautions, such as to:

• Remain adequately hydrated.
• Exercise the calves.
• Spend periods out of their seat.
• Avoid excess alcohol.
• Avoid tight-fitting socks or stockings.
• Perhaps use graduated compression stockings.

Advice about any more specific DVT prophylaxis should be based on relevant risk stratification and clinical judgement.

Risk category	Relevant risk factors	Suggested prophylaxis
Minimal risk	Age <40; otherwise fit and healthy.	General advice.
Low risk	Age >40; obesity; active inflammation; minor surgery within 3 days.	As above ± graduated compression stockings.
Moderate risk	Varicose veins; poorly controlled heart failure; MI within 6 weeks; oestrogen therapy (including oral contraception); polycythaemia; pregnancy/puerperium; lower limb paralysis/trauma within 6 weeks.	Consider aspirin if there is no contra-indication ± graduated compression stockings.
High risk	Previous VTE; known thrombophilia; major surgery within 6 weeks; previous stroke; malignancy; family history of VTE.	As above but consider low molecular weight (LMW) heparin in place of aspirin.

Respiratory disease

• Deciding on fitness to fly for those with pre-existing respiratory disease can be difficult.
• Those breathless at rest should not fly without oxygen.
• A simple fitness-to-fly test is the ability of a patient to walk 50 metres unaided at a normal pace, or to ascend one flight of stairs, without becoming severely dyspnoeic.However, there is no evidence base to support this test.
• If a person's oxygen saturation is equal to, or more than 95%, they do not need oxygen for flying, and there is no need for a referral to a respiratory specialist.
• Anyone with an active exacerbation of respiratory disease would be wise to wait until their respiratory condition has improved, before flying.
• Those with active respiratory infection, including both pneumonia and viral infections, should be clinically recovered and no longer infectious before they travel.
• It is often worth seeking the advice of a respiratory physician in severe or complex cases, to define criteria and relevant investigations on which a patient should be judged as fit to fly, particularly with regard to the need for oxygen during flight. A combination of history, examination, lung function tests, hypoxic challenge testing and arterial blood gases may be needed in difficult cases and in deciding on whether in-flight oxygen is needed.
• The hypoxic challenge test simulates the cabin environment in the laboratory using oxygen-nitrogen mixes. If the challenge results in a P_aO₂ of less than 55 mm Hg, oxygen is indicated during flight.
• Untreated pneumothorax is an absolute contra-indication to air travel. Travel can usually be carried out two weeks after effective treatment, provided there has been full expansion of the lung.
• Patients with stable asthma should be able to fly with no problems. However, they should keep their medication to hand. It may be advisable to prescribe a course of oral steroids for them to start if their condition deteriorates.

It is unusual for patients to be allowed to take their own oxygen supply and oxygen is usually arranged by the airline who must be aware in advance.

Pregnancy

• Due to the increasing risk of an in-flight delivery, most airlines prohibit travel after the end of the 36th week in uncomplicated singleton pregnancies. Earlier limits apply for multiple/complicated pregnancies or with a history of premature delivery. The limit for multiple pregnancy is generally 32 weeks.
• Most airlines require confirmation of dates from doctors for pregnancies >28 weeks. This should include the expected date of delivery and details that the pregnancy is progressing normally with no expected complications.
• The risk of DVT is increased in pregnancy but it is unclear how this risk is affected by flying. Sensible precautions should be taken as for any traveller and compression stockings should be considered. If there are additional risk factors for thrombosis, specialist advice may need to be taken.
• The risk of increased exposure to cosmic ionising radiation for the fetus is not thought to be significant, but is unquantifiable and must be taken at the mother's discretion. The risk may be increased if flying several times a week.

Infants and children

• The BTS advises waiting 1 week after birth before flying to ensure the infant is healthy.
• Infants born prematurely who have had complications should probably not fly under the age of 6 months post-expected date of delivery.
• Infants with a history of neonatal respiratory illness and children with chronic lung disease should have pre-flight hypoxic challenge testing.

Anaemia

• Someone with a haemoglobin <7.5 g/dL has a risk of hypoxia and an assessment of their fitness to fly should be carried out. In-flight oxygen should be considered.
• The degree of adaptation to the anaemia will affect the likelihood of problems. Patients with chronic anaemia will tolerate hypoxia better than those who have had a recent haemorrhage.
• Patients with sickle cell disease should have access to in-flight oxygen. They should not travel for 10 days following a crisis. Patients with sickle cell trait can usually travel without restriction.

Ear, nose and throat problems

• Active middle-ear infections, effusions, or recent ear surgery are contra-indications to flying unless the patient is deemed fit-to-fly by an ear, nose and throat (ENT) specialist.
• Acute sinusitis, large nasal polyps and recent nasal surgery are relative contra-indications.
• Seek advice from an otolaryngologist if uncertain.

Postsurgical patients

• Patients should not fly for 10 days following abdominal surgery.
• Flying is not advised for 24 hours after a colonoscopy or other procedures where a large amount of gas has been introduced into the colon.
• Flying is not advised for 24 hours after a laparoscopy.
• Travellers with colostomies may need to use a larger bag as intestinal distension during the flight may increase faecal output.
• Air travel should be avoided for 7 days following neurosurgery due to the possibility of residual gas being trapped in the skull.
• Interventions for retinal detachment usually involve the introduction of gas by intra-ocular injections and can cause an increase in intra-ocular pressure. Air travel should not be undertaken for 2-6 weeks depending on the type of gas used.
• Flight should be delayed for one week after other ophthalmological procedures or penetrating eye trauma.
•  Airlines have a list of guidelines outlining the minimum time before it is advisable to travel after surgery. Different airlines may have different policies.

Trauma/orthopaedics

• Patients should wait for 24 hours following application of a plaster cast, for flights of less than 2 hours and for 48 hours on longer flights because air may be trapped beneath the cast.
• If urgent travel is necessary, a bi-valved plaster cast can be used.

Neurological/psychiatric illness

• Fitness-to-fly is best considered on an individual basis and with expert advice if there is uncertainty. The freedoms of the affected individual to travel must be balanced against those of other passengers and safety considerations.
• Acutely disturbed or psychotic patients should not travel.
• Patients with controlled epilepsy can generally fly safely. However, they should be made aware of the potential seizure threshold-lowering effects of fatigue, delayed meals, hypoxia and disturbed circadian rhythm. Care should be taken that medication should not be omitted inadvertently when travelling through different time zones.

Contagious infectious disease

• This is a relative contra-indication to travel depending on the nature of the condition and its transmissibility at that phase of the illness.
• Tuberculosis is a particular concern. A passenger should have had adequate treatment and be non-infectious prior to the flight.

Diabetes mellitus

• There are no restrictions on flying with well-controlled diabetes.
• Insulin-dependent diabetics are normally required to have a letter of authorisation from their doctor to allow carriage of needles in their hand luggage. Insulin should be carried in a cool bag or pre-cooled vacuum flask.
• Insulin should not be stored in the hold as temperatures may cause it to freeze and denature.
• Special consideration needs to be given to insulin dosing regimens on long-haul flights, depending on the direction of travel and movement across time zones. Advice from a diabetes specialist may be needed. However, as a general rule:
  • When travelling east and if more than 2 hours are lost, it may be necessary to take fewer units with intermediate or long-acting insulin.
  • When travelling west and the day is extended by more than 2 hours, supplemental short-acting insulin, or an increased dose of intermediate-acting insulin may be needed.
• Sugar tablets and snacks to prevent episodes of hypoglycaemia should be carried.