In-flight medical emergencies: Who,what,and how many?

Airline travel is safe and reasonably comfortable, but many factors, including psychological stress, circadian misalignment, and pre-existing illness, can cause a passenger to become sick while flying. Older passengers may also have one or more underlying illnesses that impair their ability to adapt to a potentially stressful environment. At the same time, factors such as increasing passenger load, especially on large airplanes, combined with ultra-long duration flights between city pairs such as Auckland to Doha or Perth to London, further increase the probability that a medical emergency will occur during flight. In-flight medical emergencies present many challenges to physicians and other medical professionals as well as the cabin crew and flight crews. Understanding the pathophysiology of these events will help anyone who comes to the aid of a sick passenger.

In this issue, Epstein et al. describe the epidemiology of medical emergencies that occurred during one year on a major airline’s domestic and international flights. They found that the incidence of an in-flight medical event was approximately one in 40 flights, averaging 296 medical events per month. Overall, 26% of these incidents were determined to be an emergency, most commonly due to loss of consciousness or suspected cardiovascular events (12%); six of these emergencies were fatal. The most common minor events included syncope and gastrointestinal upset. Although several other studies have been published on this topic,^1,2 Epstein et al. have brought to light important updates that reflect our understanding of the in-flight environment and the changing demographics of commercial airline passengers. They also offer valuable advice to anaesthetists who may be asked to volunteer their assistance.

The fact that some passengers fall ill while flying is not surprising. As Epstein et al. state, a variety of factors combine to cause in-flight medical events. The first is simply statistics: over three billion people flew on commercial airlines worldwide during 2015; this corresponds to an average of over nine million passengers per day. ³ In other words, more people fly per day than live in many small cities! Secondly, although most passengers’ primary concern is the size of the seat, the cabin of a pressurized aircraft is a life support environment that induces physiologic adaptations in both passengers and crew. The pressure altitude in the cabin of transport-category airplanes is generally between 1800 and 2400 metres. The fraction of inspired oxygen is the same in the air as on the ground (approximately 0.21), but the decreased barometric pressure causes mild hypoxia in even normal passengers. Anxiety, claustrophobia, turbulence, and acceleration may further increase the risk of unexpected clinical deterioration, especially in a debilitated passenger with multiple comorbidities. These factors, combined with sleep deprivation, circadian misalignment, pre-existing cardiac or respiratory disease, and others further increase the risk of a medical event, especially during longer flights. In-flight medical events are not limited to passengers; DeJohn et al. found that a total of 173 pilots were incapacitated over a 10-year period; 23 were incapacitated due to a cardiac event and nine died as a result of their illness. ⁴

Anaesthetists who are travelling might be asked to help a sick passenger during an in-flight medical emergency. Our understanding of physiology combined with our ability to develop a new plan in the face of rapidly changing circumstances and to function as a member of a team make us uniquely qualified to assist. As Epstein et al. state, medical care on board a commercial aircraft requires that the treating physician work with whatever equipment is included in the on-board medical kit, in a small space with dim lighting. Some amount of imagination and creative use of on-board resources is therefore required. For example, the author once suspended a bag of intravenous fluid from a coat hanger that was wedged into the overhead storage bin. Interestingly, another recent review cites the limited resources on commercial airplanes and concludes that expertise in wilderness medicine might also be helpful. ⁵ All airlines work with a ground-based medical consultation service (e.g. MedAire, Phoenix, Arizona, USA) that will offer valuable assistance to the physician volunteer and will also advise the volunteer and flight crew if diversion is considered. Treatment goals during flight are different than on the ground: the goal is not to cure the patient, but rather to stabilize the medical condition to the extent possible while making a decision to continue the flight or divert. ⁶

Although the majority of in-flight events are not life-threatening, some, such as cardiac arrest or anaphylaxis, can be fatal if they are not promptly treated. Perhaps the most difficult decision that a physician volunteer may make is whether or not to recommend that the flight be diverted. Although the decision to divert the aircraft is ultimately made by the pilot in command, he or she will almost always consult with ground-based medical consultation services and on-board medical volunteers. Factors that should be considered include whether escalating medical care will help the patient, the ability to stabilize the patient’s condition with resources that are available on board, the amount of flight time that will be saved by diverting, and the proximity of medical resources to the intermediate airport. This must be balanced with consideration of operational factors such as weather, fuel load, and the availability of services at potential airports for diversion. Logistical issues such as air traffic control and diplomatic landing rights also affect the decision. Diversion thus requires balancing the safety of the other passengers and crew against the condition of the sick passenger and the possibility of an improved outcome. ⁶

Epstein et al. also raise important legal and ethical issues. The United States, the European Union, and Australia offer varying degrees of protection for physicians who volunteer their services. The Australian Law of Negligence, for example, does not universally exempt a physician who offers assistance. In contrast, the United States’ Aviation Medical Assistance Act limits the liability of physicians who assist sick passengers as long as they do not request compensation for their services. The applicability of these laws on an airplane can be complex: according to the Convention on International Civil Aviation, aircraft have the nationality of the country in which they are registered. ⁷ In other words, a passenger on an Australian-registered Qantas airplane is probably subject to Australian law even if that airplane is in the United States. If the airplane is not in international airspace, however, the country in which the event occurs may also try to assert jurisdiction. Because each country has its own statutes regarding medical liability, the authors wisely suggest that physicians ensure that their liability insurance will cover them for potential lawsuits related to their assistance with flight-related medical emergencies (as noted by Epstein et al. regarding their own study, this editorial is also presented for the purposes of discussion only; it is not based on formal legal advice, and provides no guarantees or warranties to any third party). Ethical concerns may be much more difficult to resolve. Certainly, no responsible physician would care for a patient after drinking an alcoholic beverage. Suppose, however, that the only physician on board has had one drink and is asked to help a passenger who is gravely ill? Nearly every physician has come to work with a minor illness. Is an anaesthetist less impaired by mild gastrointestinal upset while working in the theatre than when s/he is suffering from motion sickness while assisting a passenger? These questions have yet to be answered.

Lastly, Epstein et al. cite the lack of comprehensive, international data regarding in-flight medical emergencies. This is an important point: each airline and each ground-based medical consulting service maintains its own database, but this information is rarely shared. Because the airlines are primarily concerned with getting the passenger to definitive medical care, there is little data about long-term outcomes. This highlights the importance of an international registry of in-flight medical events. ⁸ Physicians travel routinely and are often asked to render assistance, but few understand the unique challenges posed by treating a passenger on a commercial airplane. ⁹ Epstein’s study offers valuable information that will help physician volunteers and their patients and contributes to the safety of our global city in the sky.