key: cord-1007176-bipaceqy
authors: Silverman, Danielle; Gendreau, Mark
title: Medical issues associated with commercial flights
date: 2009-02-21
journal: Lancet
DOI: 10.1016/s0140-6736(09)60209-9
sha: a699959af2a8f69be27e61bb1f4039fc21993686
doc_id: 1007176
cord_uid: bipaceqy

Almost 2 billion people travel aboard commercial airlines every year. Health-care providers and travellers need to be aware of the potential health risks associated with air travel. Environmental and physiological changes that occur during routine commercial flights lead to mild hypoxia and gas expansion, which can exacerbate chronic medical conditions or incite acute in-flight medical events. The association between venous thromboembolism and long-haul flights, cosmic-radiation exposure, jet lag, and cabin-air quality are growing health-care issues associated with air travel. In-flight medical events are increasingly frequent because a growing number of individuals with pre-existing medical conditions travel by air. Resources including basic and advanced medical kits, automated external defibrillators, and telemedical ground support are available onboard to assist flight crew and volunteering physicians in the management of in-flight medical emergencies.

Fitness for air travel is a growing issue because many passengers are unaware of health implications associated with commercial air travel. Almost 2 billion people travel by air every year, 1,2 and physicians are now expected to identify individuals unfi t for air travel and give them advice. More than 95% of individuals with health problems who have to travel by air would like to receive more medical advice from their physician. 3 Also, the age of travellers is increasing and long-haul aircrafts-such as the Airbus A380 and Boeing 777 LR-are now capable of extending fl ight times to 18-20 h; therefore, an increasing number of travellers with various underlying medical conditions could face environmental and physiological changes associated with the fl ight. Here, we review the health issues associated with commercial air travel.

Cabin pressure can aff ect the health and wellbeing of passengers in many ways, including hyobaric hypoxia aff ecting those with pre-existing respiratory conditions and heart failure, and gas expansion within body cavities and medical devices.

Although commercial fl ights usually cruise at altitudes of 7010-12 498 m above sea level, the passenger cabin is pressurised to an altitude of 1524-2438 m. Most regulatory governmental agencies require the cabin altitude not to exceed 2438 m. [4] [5] [6] Most healthy individuals tolerate this cabin pressure; however, a study of adult volunteers simulating a 20-h fl ight showed that the frequency of reported complaints associated with acute mountain sickness (fatigue, headache, lightheadedness, and nausea) increased with increasing altitude and peaked at 2438 m, with most symptoms becoming apparent after 3-9 h of exposure. 7 Cabin pressurisation to 2438 m reduces the atmospheric pressure of the cabin, resulting in a concomitant decrease of arterial oxygen partial pressure (PaO 2 ) from 95 mm Hg to 60 mm Hg at the maximum cabin altitude of 2438 m. 8 In healthy passengers, these pressures lead to a 3-4% decrease in systemic oxyhaemoglobin saturation (the corresponding PaO 2 value remains within the fl at portion of the oxyhaemoglobin dissociation curve) (fi gure). 5, 7 However, many passengers with pre-existing cardiac, pulmonary, and haematological conditions have a reduced baseline PaO 2 , so reduced cabin pressure leads to further reduction of oxygen saturation, which lowers further with increasing fl ight times (fi gure). 8, 9 The decreased oxygen saturation can exacerbate medical conditions. 2, 4, 9, 10 For example, a recent prospective observational study showed that 18% of passengers with chronic obstructive pulmonary disease have at least mild respiratory distress during a fl ight. 11 Several methods are available to assess the need for in-fl ight oxygen (panel 1). 9, 10, 12, 13 Oxygen supplementation is recommended for passengers with either a resting oxygen saturation of 92% or lower (PaO 2 ≤67 mm Hg) or if the expected in-fl ight PaO 2 is less than 50-55 mm Hg. 9 Guidelines from the British Thoracic Society (BTS) 9 suggest hypoxic-challenge testing in individuals with resting oxygen saturations of 92-95% at sea level who have additional risk factors, such as hypercapnia or abnormal spirometry. The Aerospace Medical Association (AsMa) guidelines suggest sea-level blood gas determination or pulmonary-function testing with hypoxic-challenge testing as the gold standard, and recommend in-fl ight oxygen for individuals with a sea-level PaO 2 of 70 mm Hg or lower, or with an expected in-fl ight PaO 2 of 55 mm Hg or lower. 10 However, some evidence suggests that these guidelines might need revision because predictive equations often inaccurately estimate in-fl ight PaO 2 . 2, 9, 12, [14] [15] [16] Additionally, recent work has shown that initial sea-level oxygen saturation poorly identifi es individuals at risk of desaturation below 90% during either hypoxic-challenge testing in the laboratory 17, 18 or routine commercial fl ights. 15, 17 No studies that assess individuals with heart failure during commercial air travel exist; however, several small studies have shown that people with chronic heart failure tolerate altitudes up to 2500-3000 m. 19, 20 BTS or AsMa guidelines should be followed with patients aff ected by heart failure who have to travel by air.

Several options exist for passengers needing medical oxygen during air travel. Compressed oxygen supplied by the airline is available for individuals with a physician's statement of need and prescription. Since 2005, portable oxygen concentrators, which concentrate oxygen in ambient air by removing nitrogen content, have become available as an alternative to traditional oxygen cylinders. Passengers should possess a signed doctor's statement of medical need and notify the airline of their intention to use portable oxygen concentrators before travelling. 21 Because of a modifi cation in the US Government Air Carrier Access Act in May, 2008, all US-based air carriers and foreign air carrier fl ights that begin or end in the USA have to accommodate passengers who need portable oxygen concentrators. 22 Gas in body cavities is also aff ected by cabin pressure. According to Boyle's law, the volume that a gas occupies is inversely proportional to the surrounding pressure. Thus, at the low cabin pressures associated with cruising altitudes, gas in body cavities expands by 30%. 6, 10, 23 For healthy passengers, this expansion can result in minor abdominal cramping and barotrauma to the ears in certain circumstances. However, passengers who have undergone recent surgical procedures are at increased risk of problems related to gas expansion, and many anecdotal reports, including those of bowel perforation 24 and wound dehiscence, 25 have been published. Guidelines recommend delaying air travel for 14 days after major surgical procedures. 10, 23 Individuals with bowel obstructions or diverticulitis are advised to wait 7-10 days before air travel. 10, 23 Passengers who scuba dive also have an increased risk of decompression sickness if they fl y too soon after diving. The diver's alert network recommends a 12-h interval between diving and air travel for divers who make a dive per day without decompression. Divers participating in several dives per day, or a dive requiring decompression, should wait 24 h before air travel. 10, 23 Gas expansion also aff ects medical devices, such as pneumatic splints, feeding tubes, urinary catheters, and cuff ed endotracheal or tracheostomy tubes. Gas-expansion concerns in these devices can be eliminated by instillation of water rather than air during air travel. 6, 26 

The relation between long-haul fl ights (>8 h) and increased risk of venous thromboembolism has generated great interest in both medical publications and the media. Overall, studies show an association between venous thromboembolism and long-haul air travel, with risk up to four-fold, depending on study methods. [27] [28] [29] [30] [31] [32] [33] Risk peaks when fl ight duration is more than 8 h; 34-36 a population-based study showed that risk started to increase when fl ight duration exceeded 4 h. 32 Business-class versus economy-class travel has no eff ect on venous thromboembolism incidence. 37 A systematic review of publications on air-travel venous thrombo embolism calculated a pooled odds ratio (OR) 

The maximum cabin altitude of 2438 m can be simulated at sea level with a gas mixture containing 15% oxygen in nitrogen. Individuals breathe the hypoxic gas mixture for 20 min while oxygen saturation is monitored. Arterial blood gases are also measured before and at the end of the test. An individual needs in-fl ight oxygen if PaO 2 falls below 50 mm Hg or if the oxygen saturation measured via pulse oximetry falls below 85%.

PaO 2 at altitude can be estimated with several published predictive equations, which use values of ground-level PaO 2 and lung-function measurements to predict in-fl ight PaO 2 : • In-fl ight PaO 2 =0·453×ground-level PaO 2 (mm Hg)+0·386 (FEV 1 % predicted)+2·44 • In-fl ight PaO 2 =0·519×ground-level PaO 2 (mmHg)+11·855xFEV 1 (L)-1·760 FEV₁=forced expiratory eff ort in 1 second. of 1·59 (95% CI 1·04-2·43) from case-control studies 27,38-41 and a relative risk of 2·93 (95% CI 1·5-5·58) from several prospective controlled cohort studies. 38, 40 These results are consistent with those of the population-based (MEGA) study (OR 1·7, 95% CI 1·0-3·1). 32 Another population-based study of 9000 business travellers followed for 4·4 years showed an absolute risk for venous thromboembolism of one every 4656 fl ights (incidence rate ratio 3·2, 95% CI 1·8-5·6). 33 Risk increased with increasing number of fl ights during the fi rst 2 weeks after a fl ight and when other traditional risk factors for venous thromboembolism were present. Several factors-such as immobility, dehydration, hypobaric hypoxia-and individual risk factors (obesity, malignancy, recent surgery, and history of hypercoagulable states) explain why the risk of venous thromboembolism increases with air travel. 40, 42 Immobilisation has been linked to 75% of air-travel cases of venous thromboembolism, with the long-fl ight thrombosis study (LONFLIT) showing the greatest frequency of venous thromboembolism occurring in non-aisle seating where passengers tend to move less. [42] [43] [44] [45] Dehydration can increase risk of venous thromboembolism due to haemoconcentration and hyperviscosity, potentially leading to hypercoagulable states. 46 Several studies have provided evidence of dehydration or increased lower-limb oedema in healthy people during long-simulated fl ights. 47, 48 Hypobaric-chamber studies have not consistently shown that the mild hypobaric hypoxic changes during a fl ight lead to increased activation of coagulation in healthy individuals with no thrombophilia compared with that in individuals seated and not moving at ground level. 5, 46, 49 Thrombophilia or oral contraceptive use substantially increase the risk of developing venous thromboembolism. 29, 32, 50 In the MEGA study, 32 factor V Leiden increased this risk by 14 times (OR 13·6, 95% CI 2·9-64·2), and thrombophilia or use of oral contraceptives increased risk 16 times (16·1, 3·6-70·9) and 14 times (13·9, 1·7-117·5), respectively. 29 Recommendations to reduce the risk of developing venous thromboembolism during air travel are based more on common sense than on evidence and include: being well hydrated, reducing alcohol and caff eine consumption, changing positions or walking throughout the cabin, and doing periodic calf-muscle exercises to reduce venous stasis. Use of graduated compression stockings with an ankle pressure of 17-30 mm Hg can reduce risk during air travel, as shown by a meta-analysis, in which only two of 1237 individuals who wore compression stockings had venous thrombosis compared with 46 of 1245 individuals who did not wear them. 51 Compression stockings therefore are recommended for travellers prone to immobility. [51] [52] [53] Anticoagulant thromboprophylaxis in the context of air travel is growing but no formal guidelines exist. One survey done by thrombosis and haemostasis professionals showed major diff erences in the use of prophylactic measures for air travel. 54 Many clinicians seem to recommend aspirin before air travel for individuals at moderate risk of venous thromboembolism. However, because of scarce evidence showing substantial benefi t, aspirin is not recommended alone as prophylaxis for any air traveller. 41, 43, 52, 55 Although randomised trials have shown benefi t of low-molecular-weight heparin as thromboprophylaxis for air travellers who are at moderate risk for venous thromboembolism and do not take routine anticoagulant drugs, 43, 56 its routine use in circumstances other than those for air travellers at high risk of venous thromboembolism remains contro versial. 41, 52 Overall, use of physical and pharmacological thromboprophylaxis should be based on an individual risk assessment. The table summarises evidence-based guidelines updated in 2008 by the American College of Chest Physicians conference on antithrombotic and thrombolytic therapy. 52

Cosmic radiation comes from outside the solar system and from particles released during solar fl ares. Intensity of radiation depends on the year (due to solar cycles), altitude, latitude, and length of exposure. Because many types of cancer might be linked to cosmic radiation-especially breast cancer, skin cancer, and melanoma-eff ects of radiation on fl ight crews and frequent air-travellers are of concern. 58, 59 In 1991, the International Commission on Radiological Protection (ICRP) declared cosmic radiation an occupational risk for fl ight crews, which led to exposure monitoring and guidelines to reduce crew annual exposure to 20 mSv, which is more than double the exposure of most crews. 60 

should be restricted to 1 mSv per year in the population, but air-travel-related cosmic-radiation exposure does not have a specifi c limit. 63 The UK Civil Aviation Authority (CAA) and the European Joint Aviation Authority (JAA) require aircraft capable of fl ying at altitudes greater than 15 km, to actively monitor radiation levels, so that they can lower fl ying altitude as needed. However, this regulation is currently not relevant to commercial aviation because no commercial aircraft fl y at such altitudes. 7 A solar-radiation alert system monitors high-particle intensity from solar radiation, and the US Federal Aviation Administration (FAA) issues a solar-radiation advisory to air carriers via the national oceanic and atmospheric administration (NOAA) weather wire service when solar fl ares might cause increased radiations at commercial-aircraft altitudes. 64 Data for increased cancer risks specifi cally due to cosmic radiation in crew members are inconclusive. 62, [65] [66] [67] [68] No studies have been done to assess the health consequences of cosmic-radiation exposure during air travel in the general population. However, even the most-frequent air travellers are unlikely to be at risk. 69 Recommendations need to be in place for pregnant women because the fetus is exposed to the same radiation dose as the mother. 70 The ICRP recommends a radiation limit of 1 mSv during the whole pregnancy, whereas the National Council on Radiation Protection and Measurements recommends a monthly limit of 0·5 mSv. These recommendations limit pregnant crew members and frequent air travellers, because fl ying roughly 15 long-haul round trips, for example, can expose a fetus to more than 1 mSv. 61 To avoid risk to the fetus, the FAA recommends pregnant crew members to take short, low-altitude, low-latitude fl ights, and the CAA requests that employers of a pregnant crew member schedule her fl ights so that she remains under the 1-mSv limit. 7, 59 Pregnant women, and air travellers in general, can access the solar-radiation alert system online before travelling and change fl ight days accordingly.

Jet lag is a temporary circadian-rhythm disorder associated with long-haul fl ights, characterised by daytime fatigue, sleep-wake disturbances, decreased appetite, constipation, and reduced psychomotor coordination and cognitive skills. [71] [72] [73] Jet lag is due to desynchronisation between the body's internal clock mechanism, residing within the suprachiasmatic nucleus of the hypothalamus, [74] [75] [76] and the new light-dark cycle caused by abrupt time-zone changes. 72, 73, [77] [78] [79] The degree and severity of jet lag is infl uenced by both fl ight direction and number of time zones crossed. 72, 80 Westward travel lengthens the traveller's day, thereby causing a phase delay in the circadian rhythm, whereas eastward travel shortens the day and causes a phase advance. 72, 73, 80 Travellers have greater diffi culty falling asleep after an eastward travel than after a westward travel because of the internal clock's natural tendency to resist shortening the 24-h day cycle. 79, [81] [82] [83] Re-entrainment (synchronisation) typically takes one day for every time zone crossed westward or 1·5 days for every time zone crossed eastward. 72, 73, 80, 81 Panel 2 lists various therapies available to keep jet lag to a minimum. Exogenous melatonin is the gold standard treatment for jet-lag symptoms. 73, 83, 89, 90 When taken in the evening, melatonin phase advances the circadian clock, whereas early morning administration phase delays the circadian rhythm. 73, 90 Various treatment regimens have been recommended, but a Cochrane meta-analysis of ten trials concluded that taking 0·5-5 mg of melatonin at the desired destination bedtime is eff ective for reducing or preventing jet lag. 83 Use of bright-light exposure to adjust circadian rhythm has shown confl icting results and its benefi t depends on • Westbound: go to sleep 1 h later than usual and be awake 1 h later than usual 3 days before travelling • Eastbound: go to sleep 1 h earlier than usual and be awake 1 h earlier than usual 3 days before travelling

For the solar-radiation alert system see http://www.sec. noaa.gov/ combination with other therapies, such as bedtime adjustment or melatonin. [91] [92] [93] Simulation studies showed a benefi t of gradually advancing the sleep cycle by going to sleep 1 h earlier than usual every day for 3 days before travelling eastward, combined with morning bright-light exposure, in an attempt to phase advance the circadian rhythm. 87, 92 For westward travel, one small randomised controlled study of 20 individuals combined bedtime adjustment with timed bright-light versus dim-light exposure after westward travel, and showed larger phase delays in the bright-light group than in the dim-light group (2·59 h vs 1·5 h, p <0·02), but no signifi cant diff erence in sleep effi ciency or self-reported symptoms of jet lag. 93

Air travellers spend long periods in enclosed spaces, which facilitates the spread of infectious diseases. 103 and small pox. 104 Although less-serious outbreaks-such as the common cold or some viral syndromes-have not been reported, they can occur. Lack of reporting is likely to be the result of incubating periods of many infections being longer than the fl ight. One prospective questionnaire study of air travellers going from San Francisco to Denver during the winter months showed an upper-respiratory tract infection frequency of 3-20% depending on the reporting methods. 105 PCR assays to study atypical bacteria and respiratory viruses in 155 air travellers showed that not many travellers had the same viral profi le and no association existed between any pathogen and a particular airport, suggesting that travellers acquired their viruses before rather than during the fl ight. 106 Most commercial aircrafts re-circulate up to 50% of the cabin air and use high-effi ciency particulate air fi lters. One study showed no signifi cant diff erence in self-reported infection rates in aircrafts that use these fi lters compared with those in aircrafts that use a single-pass cabin ventilation system. 105 Risk of onboard transmission of infection is mainly restricted to individuals with either close personal contact or seated within two rows of an index passenger. 1, 107 However, on Air China fl ight 112, 22 passengers and crew member developed probable onboard severe acute respiratory syndrome-associated coronavirus (SARS-CoV) infection. 97 The 2002-03 SARS epidemic indicated that commercial air travel has an eff ect on infectious-disease spread. WHO estimates that 6·5 passengers per million who travelled aboard commercial fl ights originating from regions of active transmission during the outbreak were symptomatic with probable SARS. 108 Overall, 40 fl ights carried 37 probable SARS-CoV source cases during the outbreak, resulting in 29 probable onboard secondary cases. 108 Whether reducing the number of fl ights during a largescale epidemic or pandemic would slow the spread of an infectious-disease outbreak remains unclear. 109, 110 An observational study, however, showed that the peak date of the US infl uenza season was delayed 13 days after the terrorist attacks of Sept 11, 2001 , consistent with a greatly reduced number of fl ights during that time. 111 This, together with other modelling studies, suggest that fl ight limita tions might slow the spread of pandemic infl uenza by several weeks, thereby providing time for mass vaccination of the population and contingency plan setup. 111

Calculation of the exact incidence of in-fl ight medical events for commercial air travel has always been diffi cult, mainly because air carriers are not obliged to report in-fl ight medical events, and no national or international database exists. Scarce data suggest an incidence of 1 in 10 000-40 000 passengers (about 50-100 in-fl ight medical events per day) aboard US-registered airlines. 112 British Airways health services reported 31 200 medical incidents aboard their aircrafts during 2007, with 3000 being deemed serious. 113 Many in-fl ight medical events arise aboard commercial airlines and most are minor. 6, 114 Cardiac, neurological, and respiratory complaints are the most serious in-fl ight medical events, with cardiac and neurological complaints accounting for most diversions. 114 Passengers older than 70 years have the highest rates of in-fl ight medical events, 114 but the mean age of passengers with an in-fl ight medical event is 44 years for men and 49 years for women. 6, 112 According to British, Canadian, and US laws, medical professionals are not required to volunteer assistance during an in-fl ight medical event, unless they have a pre-existing clinical relationship with the passenger. In contrast, physicians in Australia and many Asian, European, and middle east countries are required to provide assistance. 6 For international fl ights, the country where the aircraft is registered has jurisdiction, except when the aircraft is on the ground or in sovereign airspace. 6, 112 Medical assistance during an in-fl ight medical event is protected under Good Samaritan laws, and no physician has ever been held liable for his or her actions while providing medical care. The 1998 US Aviation Medical Assistance Act limits liability for volunteering physicians under the assumption that they act in good faith, receive no monetary compensation, and provide reasonable care. This law pertains to events that occur within US airspace and aircraft registered within the USA. 6 Gifts, such as seat upgrades and liquors, are not considered compensation. Furthermore, many airlines indemnify volunteering physicians, and the captain should provide written confi rmation on request. 112 Commercial aircraft have medical kits (1-4 fi rst-aid kits and at least one enhanced emergency medical kit), as required by aviation regulatory agencies. 6, 112 Emergency medical kits vary from carrier to carrier and can be extensively complex (panel 3). Most commercial fl ights also carry an automated external defi brillator, and some models have a screen showing a basic rhythm strip. Most commercial air carriers use on-ground telemedical assistance to medically assess at the gate passengers who seem unfi t for travel, and to provide medical advice and support during in-fl ight medical events. Several companies and academic medical institutions provide 24-h ground-to-air medical support and have groundbased physicians, who also advise the fl ight deck on the best diversion location and arrange emergency personnel to meet the aircraft.

Clinicians who off er medical assistance during a fl ight should know that their role is to assist the fl ight crew and

• Be prepared to show medical credential (eg, licence) or answer questions about degree or training • Act within your abilities • Obtain consent from the aff ected passenger. Assume implied consent when passenger is incapacitated or unresponsive • Do not fear litigation. Although physicians have been deposed, no litigation has ever been brought forward against a responding physician • Request and establish communication with the airline's ground medical support for advice and consultation regardless of how minor or serious the in-fl ight medical event is • Request the enhanced emergency medical kit (many airlines will initially only off er the basic fi rst-aid kit) but do not open it unless needed. Each kit has a placard listing the contents of the kit • Recommend diversion of the aircraft if you believe it is needed. Recommendation to divert the aircraft should be considered if a passenger has chest pain, shortness of breath, severe abdominal pain that does not improve with initial treatment interventions, cardiac arrest, acute coronary syndrome, severe dyspnoea, stroke, refractory seizure, severe agitation, or if a passenger is persistently unresponsive • Never offi cially pronounce a passenger dead, even if you assess that resuscitation is futile and cease treatment, especially on international fl ights not to take complete control of the situation. The captain of the aircraft has the ultimate authority (panel 4). In case of violent or unruly passengers, volunteering physicians might need to assist in chemical or physical restraint. If chemical restraint is used, physicians should consider that passengers could have ingested alcohol or other substances that might cause oversedation or other eff ects. 116 Panel 5 lists general guidelines for the initial management of common in-fl ight medical events.

Airlines have the right to refuse passengers who are unfi t to fl y for medical reasons. 6, 119 Many conditions contraindicate air travel and passengers who cannot tolerate hypoxia or pressure changes should not fl y (panel 6). Passengers should be able to walk a distance of 50 m and climb one fl ight of stairs without angina or severe dyspnoea. 6 If a passenger needs oxygen, he or she requires physician documentation stating fi tness to travel at 2438 m. Passengers bringing needles and syringes into the cabin should possess documentation of need and carry the medication that requires that equipment with pharmacy-labelled identifi cation. 124 Some passengers might also need a qualifi ed medical escort, such as passengers whose fi tness to travel is in doubt due to possible exacerbation or instability of chronic disease or passengers who have organ failure requiring transplantation. 119 Many air carriers have limited transport of passengers on stretchers or those unable to sit upright in a seat. 125 Numerous air ambulance services and clinics off er physician-assisted or nurse-assisted escorts for commercial air fl ights, and physicians or passengers can call airlines for assistance.

Passenger health and wellbeing during commercial air travel continues to evolve. Cabin air quality remains an issue, and it has been linked to passenger and fl ight crew complaints of dry eyes, stuff y nose, and skin irritation, as well as headaches, lightheadedness, and confusion. 126 Peer-reviewed studies on the eff ect of vaporised organic compounds, such as tricresyl phosphate, that have led to reported cases of crew and passenger incapacitation are needed. These compounds are the result of vaporised jet oils that can mix with air entering the aircraft cabin. Several research groups, such as the cabin air-quality reference group and the Australian civil aviation safety authority, are addressing knowledge gaps on health eff ects of cabin air, including the role of vaporised organic compounds. The American society of heating, refrigerating, and air conditioning engineers-an industry leader in developing indoor air-quality standards-set, for the fi rst time, new air-quality standards in commercial aircrafts. The new standards also address chemical, physical, and biological contaminants that aff ect cabin air quality. How these standards will be adopted by aviation and governmental regulatory agencies remains unclear. At present, no regulations by the CAA, FAA, or JAA exist requiring use, certifi cation, or maintenance of high-effi ciency particulate air. New aircrafts, such as the Airbus A380 and Boeing 787, are being designed to operate at cabin altitude of 1829 m compared with the current altitude of 2438 m, in addition to having improved cabin air quality and passenger seating. These changes will improve passenger wellbeing and comfort.

How individuals with compromised cardiac and pulmonary function can endure long air travel needs to be assessed, and current screening guidelines should undergo re-assessment. Furthermore, absence of a globally accepted guideline, and major diff erences in the use of prophylactic measures by clinicians for air-travel-related thrombosis 54 emphasise the need for additional studies on interventions and clear guidelines on prevention of air-travel-related venous thrombosis.

The molecular basis for circadian-rhythm disorders has been recently clarifi ed and future clinical application might lead to new treatments for jet lag.

The risk that commercial aircrafts are vehicles of infl uenza pandemic spread is real and opportunities exist to keep the risk to a minimum. The international air-transport association, in partnership with WHO and other stakeholders, have established guidelines for aviation-industry operations during pandemic infl uenza outbreaks to keep commercial air-travel spread to a minimum. These include communication of the risk to the population, establishment of national passenger exit screening from outbreak regions, and increasing airline preparedness (in-fl ight illness and aircraft cleaning). 127, 128 In-fl ight medical events are projected to increase and AsMa encourages the creation of a database, but many air carriers are reluctant to participate. Commercial space travel is projected to start within the next decade and aerospace medical societies have set up subcommittees to address the unique medical conditions associated with civilian space travel.

In the modern travel era, clear understanding of the medical consequences of commercial fl ights has become increasingly important. Individuals need to be aware of the possible medical complications of air travel, and physicians should identify people at potential risk from air travel and advise them of any necessary treatments to travel safely.

We declare that we have no confl ict of interest.

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Eff ect of low-dose temazepam on physiological variables and performance tests following a westerly fl ight across fi ve time zones

Evaluation of pharmacological aids on physical performance after a transmeridian fl ight

Advancing human circadian rhythms with afternoon melatonin and morning intermittent bright light

Time zone change syndrome

Melatonin shifts human circadian rhythms according to a phase-response curve

Melatonin as a chronobiotic

Field trial of timed bright light exposure for jet lag among airline cabin crew

Prefl ight adjustment to eastward travel: 3 days of advancing sleep with and without morning bright light

Light visor treatment for jet lag after westward travel across six time zones

An outbreak of infl uenza aboard a commercial airliner

Outbreak of infl uenza-like illness [corrected] related to air travel

Low risk of measles transmission after exposure on an international airline fl ight

Transmission of the severe acute respiratory syndrome on aircraft

A case of in-fl ight transmission of severe acute respiratory syndrome (SARS): SARS serology positive

Exposure to Mycobacterium tuberculosis during air travel

Exposure of passengers and fl ight crew to Mycobacterium tuberculosis on commercial aircraft

Salmonellosis outbreak on transatlantic fl ights; foodborne illness on aircraft: 1947-1984

Food-poisoning and commercial air travel

Probable transmission of norovirus on an airplane

Aircraft cabin air recirculation and symptoms of the common cold

Spectrum of viruses and atypical bacteria in intercontinental air travelers with symptoms of acute respiratory infection

Tuberculosis and air travel: guidelines for prevention and control

Department of Communicable disease Surveillance and Response. Consensus document on the epidemiology of severe respiratory distress syndrome (SARS). WHO/CDS/CSR/2003.11. Geneva: World Health Organization

Mitigation strategies for pandemic infl uenza in the United States

Delaying the international spread of pandemic infl uenza

Empirical evidence for the eff ect of airline travel on inter-regional infl uenza spread in the United States

Commercial aviation in-fl ight emergencies and the physician

Cabin fever

An evaluation of in-fl ight medical care in the U.S

Emergency medical kit for commercial airlines: an update

Airline passenger misconduct: management implications for physicians

Top 10 in-fl ight medical emergencies

Oxford Handbook of Accident and Emergency Medicine

Prefl ight medical clearance of ill and incapacitated passengers: 3-year retrospective study of experience with a European airline

Long-distance air travel soon after an acute coronary syndrome: a prospective evaluation of a triage protocol

World Health Organization. International travel and health. Situation as of 1

Safety of air travel following acute myocardial infarction

Medical Manual 1st ed. International Air Transport Association

Fact sheet: steps taken to ensure new security requirements preserve and respect the civil rights of people with disabilities

International aeromedical evacuation

Health and perception of cabin air quality among Swedish commercial airline crew

Pandemic infl uenza: a note on international planning to reduce the risk from air transport

Guidelines for states concerning the management of communicable disease posing a serious public health risk. International Civil Aviation Orgaization, Montreal Canada

The list is based on references 10 and 120-123.