The true incidence of in-flight medical events is unknown given that there are no standards or minimal requirements for reporting by airlines. The US National Transportation Safety Board requires medical emergencies to be reported if the event requires 48 hours of hospitalization, involves injury to internal organs, or fractures (excluding nose, finger, or toe fractures) [1]. Most studies that evaluate in-flight emergencies acquire data from on-ground medical communication center records. According to one study, significant medical emergencies occur in one passenger per 10,000–40,000 passengers [2]. Another study found that the incidence of reported medical emergencies was one per 604 flights [3]. As the median age of the general population continues to rise and airlines can carry more people per aircraft over further distances, the incidence of in-flight emergencies will likely increase in frequency and severity. Medical professionals should be prepared to face this situation.

Prior to World War II, most American flight attendants were nurses who were able to handle nearly all in-flight medical emergencies [5]. When this standard changed, the need for medical professional volunteers became increasingly important. Emergency Medicine providers undergo training that allows them to be particularly effective in managing undifferentiated medical problems that may require immediate intervention. This does not mean that the in-flight environment is not still very challenging, as access to diagnostic and treatment modalities is very limited. Fortunately, most medical problems that occur on flights are self-limited and resolve without major treatment or diversion of flight [3]. The mortality rate for in-flight emergencies is ~0.3–1.3% [3].

Aviation agencies generally provide either mandates or guidelines as to the medical equipment that must be available on commercial airline flights. In the United States, it is mandated that all commercial airline flights that require the presence of a flight attendant and have a payload greater than 7500 lbs have onboard at least one first aid kit, an emergency medical kit, supplemental oxygen, and an automated external defibrillator (AED) [4].

There is no legal requirement in the United States, Canada, or the United Kingdom for medical professionals to volunteer when the flight crew requests assistance with an ill passenger. However, Australia and multiple countries within the European Union require medical professionals to assist with in-flight emergencies [5, 6]. The question of which country’s laws apply is a very complicated one without a clear answer. The country in which the airline is based, the flight departure country, and the flight arrival country all have a potential argument to support their laws’ applicability. Many argue that medical professionals have an ethical obligation to assist as able, but as above, this obligation is largely not codified.

Providers may hesitate to volunteer to help with in-flight medical emergencies due to concern for malpractice liability when offering assistance. However, this concern should not dissuade medical professionals from assisting in these situations. The 1998 Aviation Medical Assistance Act Good Samaritan Provision largely protects health-care professionals from legal liability (at least within the United States).

Airlines are not considered a covered entity as defined by HIPAA, and so medical providers are able to legally speak to the flight crew and ground-based consultants about the patient’s medical issues [11]. However, the provider should still attempt to protect the patient’s privacy and modesty as much as possible during an in-flight emergency.

Most commercial airlines have a cruising altitude of ~30,000–45,000 feet above sea level. This altitude allows for better fuel efficiency, less turbulence, and lower chance of inclement weather [11]. For perspective, Mount Everest is ~29,000 feet above sea level. The passenger cabin is pressurized to be equivalent to approximately 6000–8000 feet above sea level [1]. This is comparable to a small peak by mountain standards but is still significantly higher than the elevation at which most people live. An aircraft structure made suitable to allow a passenger cabin to be pressurized to sea level pressure would be too heavy to fly [11].

The low cabin atmospheric pressure affects the partial pressure of gasses. The low pulmonary artery oxygen tension that is present during flight decreases the affinity of hemoglobin for oxygen, to the point where even healthy individuals can have arterial oxygen saturations as low as 89%. The body compensates by increasing minute ventilation and cardiac output with mild hyperventilation and tachycardia. Patients who are chronic smokers or have conditions such as COPD and congestive heart failure may be unable to illicit or handle the body’s natural compensation mechanisms [1].

At the low barometric pressures within the passenger cabin, gas expands (per Boyle’s Law). Gas expanding within closed body cavities can cause pain, and passengers may complain of ear, sinus, and bowel discomfort [12]. Further, passengers must be careful about traveling within certain timeframes post intra-abdominal, eye, neurologic, and middle ear surgical procedures, as these surgeries can introduce small amounts of air into these cavities. If passengers are unaware or do not heed these restrictions, complications such as pain, wound dehiscence, or worse conditions may occur [11]. Gas expansion at low pressure can also affect air-filled medical devices such as tracheostomy tubes, feeding tubes, urinary catheters, and pneumatic splints, causing discomfort and malfunction [11].

Other circumstances present in-flight can cause a variety of medical issues. Low cabin humidity, which helps prevent airplane corrosion, can cause dry eyes and dehydration and exacerbate reactive airway disease [11, 12]. Immobility and cramped seating can put passengers at risk for thrombus formation [16]. Decompression sickness is a risk for those who have recently been scuba diving. Moreover, close contact places passengers at a higher risk of contracting communicable respiratory infections [1, 11].

General approach to any patient [3, 5, 8]

The most valuable diagnostic tool at your disposal is the one that you carry with you everywhere; your brain! History and physical exam are the major diagnostic clues for in-flight emergencies. However, completing a high-quality physical exam can be difficult due to limited space, poor light, and a noisy cabin [11]. In the United States, emergency medical kits must be equipped with a stethoscope and sphygmomanometer, but that is the extent of mandated diagnostic tools. Some airlines may carry medical kits with other supplies such as a glucometer or a thermometer, but this is not required. Further, some automated external defibrillators (AED) carried by airlines may have telemetry capabilities that can be used for cardiac monitoring in a nonarrest situation, but the sophistication of the AED is not standardized between airlines. It may be possible to utilize equipment such as a glucometer from another passenger, but always consider the cleanliness of the device and the possibility of blood-borne pathogen risk [13, 16].