Aerospace Medicine

AS WE REACH the brink of the 21st century, technological advances are creating new demands and new opportunities in aerospace medicine to address the health needs of military and civil aircrew, astronauts, ground support personnel, and airline passengers. Two areas of aerospace medicine are of particular general interest: the medical care of passengers aboard commercial aircraft and the application of telemedicine, used in the space program since the 1960s, to patient care on Earth.

During the past few years, there has been a call from Congress, the public, and the media for US commercial airlines to carry more medications in onboard emergency medical kits (EMKs) as well as automatic external defibrillators (AEDs). With predictions that the number of US airline passengers will increase from 500 million to 800 million over the next decade and the likelihood that an increasing number will be elderly or have a preexisting illness, assessing the need for in-flight medical care becomes especially important.¹ However, developing rational recommendations for aircraft medical equipment is complicated by the lack of a database that documents the frequency, type, and outcomes of in-flight medical events.

Currently the Federal Aviation Administration (FAA) mandates that each aircraft carry a first-aid kit and an EMK with 4 medications—50% dextrose, nitroglycerin tablets, injectable diphenhydramine, and epinephrine 1:1000—and minimal basic equipment (Table 1). Airlines may expand the contents of their EMKs at their discretion. In recent months American Airlines has added a number of medications to its EMKs, including anti-arrhythmics, anticonvulsants, and bronchodilators. Delta and United are also planning to augment their EMKs within the year. With this change of policy by 3 large airlines, it is probable that some of the smaller airlines will follow suit.

The use of in-flight AEDs is under review by the FAA and most US and international airlines. No regulations currently require airlines to carry AEDs. These devices are small, lightweight, and easily stowed on commercial aircraft and require little training to use. Initial training is 3 hours with 112 hours of annual refresher training.

Because of its automatic feature, an AED will deliver a defibrillatory shock only in the event of ventricular fibrillation or rapid ventricular tachycardia (not other arrhythmias). If the AED has a monitor, a treating physician could determine the type of arrhythmia and whether a flight diversion is necessary. Currently there is no federally mandated protocol that directs decisions on flight diversions for medical emergencies; each airline develops its own policy.

Two major airlines, Qantas and American, carry onboard AEDs.² American began to carry them only on over-water flights in July 1997; Qantas' experience began in 1991. Delta announced in January 1998 that it would begin carrying AEDs on its aircraft in mid to late 1998. Two small international airlines, Air Zimbabwe and Virgin Atlantic, also carry AEDs.

Only 1 report has been published to date on the in-flight use of AEDs. During a 65-month study period beginning in 1991, Qantas Airlines carried approximately 31 million passengers and reported 27 passengers with in-flight cardiac arrest. Twenty-one of these passengers had asystole or a pulseless idioventricular rhythm and 6 had ventricular fibrillation. The use of an AED successfully terminated ventricular fibrillation in 5 of these 6 passengers. Long-term survival (≥2 years) without residual neurologic impairment was reported for 2 of the 6 passengers.^{3 - 4}

In May 1997, the US House of Representatives Aviation Subcommittee held hearings on in-flight EMKs and AEDs. Experts were called to testify on in-flight medical events, recommendations for improvement of the current FAA-mandated EMK, and the need for in-flight AEDs. Based on the testimony, the Aviation Subcommittee recognized that information on in-flight medical events was incomplete. Nevertheless, the committee felt that the aviation industry and professional medical organizations should proceed and formulate policy on in-flight EMKs and AEDs based on "instinct, intuition, common sense, and the data that you have at the present time."

In compliance with the congressional request, the Aerospace Medical Association (AsMA) convened a task force of experts in aerospace medicine, emergency medicine, and other medical specialties in August 1997. Because there was no comprehensive database on which to base recommendations for in-flight medical kit contents, a survey was sent to approximately 2300 AsMA physicians that asked 3 questions about their personal experience with in-flight medical events.

Only 850 (36%) of the 2300 physicians responded to the survey. Of the 850 respondents, 533 (62%) stated that they had been called on at least once to care for a sick or injured passenger onboard a commercial airliner. The most frequent of the 1197 reported in-flight medical events were syncope or loss of consciousness; suspected myocardial infarction, angina, or chest pain; asthma; anxiety; otic barotrauma; and gastroenteritis. The respondents reported 8 in-flight deaths.⁵

Although the task force recognized that the number of respondents was small, it proposed preliminary recommendations for the contents of in-flight EMKs (Table 1) based on the results of the survey and expert opinion, and suggested that the requirements for EMKs be under ongoing review by AsMA. The task force also recommended that AEDs be carried on long-haul, over-water routes.⁵ This position was based mainly on anecdotal reports of suspected in-flight cardiac arrest. The task force felt that a broader recommendation could not be made until more information on the in-flight need for AEDs and their effectiveness becomes available.

Additional data on in-flight medical events in 1996 were collected by the Air Transport Association of America (ATA), the trade association for the principal US air carriers, from 9 of its member airlines (not identified).⁶ These events were rare, affecting 1 of 58000 passengers. In all, 10471 in-flight medical events were reported in 52 diagnostic categories(Table 2). Only signs and symptoms or presumed diagnoses were reported because there was usually no follow-up of passenger-patients once they left the airport.

If the medical equipment and contents of US air carrier in-flight EMKs are expanded, there may be growing concern on the part of the airlines and of physician-passengers regarding liability. Of the 850 physicians who returned the AsMA questionnaire, 47 (0.05%) indicated that they had not rendered in-flight medical care because of fear of litigation.⁵ Many others answered that they rendered care but that litigation was very much a concern. Although there is no record of a passenger who has brought suit against a physician in a US court related to an in-flight medical event, the possibility exists in the event of a poor outcome.⁷

The Aviation Medical Assistance Act of 1998, signed into law on April 24, 1998 (PL 105-170),⁸ requires the FAA to evaluate the regulations regarding the equipment to be carried in the airline medical kits and the training of flight attendants in the use of such equipment. The FAA must also collect data on the number of in-flight deaths for 1 year and develop a recommendation on whether AEDs should be required on commercial aircraft and in airports. The law also contains liability language intended to protect the airlines and any individual "who is licensed, certified, or otherwise qualified to provide medical care in a State," including physicians, nurses, physician assistants, paramedics, and emergency medical technicians.

Telemedicine holds the promise of real-time, interactive medical consultations with regional medical centers for physicians practicing in rural or remote areas. It has been a part of medicine's technological armamentarium for a number of years, and the space program has been developing and applying it for the care of astronauts during space flight and on space missions of long duration. Telemedicine was first used by the National Aeronautics and Space Administration (NASA) in the early 1960s when biotelemetry transmitted basic physiologic data from astronauts in orbit to NASA medical personnel. Its first major global application occurred in 1989 when NASA offered its services to Armenia after its tragic earthquake that caused thousands of casualties (Spacebridge to Armenia).⁹ The telemedicine system provided by NASA included audio, video, and facsimile capabilities via satellite links and land lines. It connected a medical facility in Yerevan, Armenia, with 4 US medical centers and provided an efficient means for Armenian physicians to consult with US physician colleagues.

Although NASA's assistance was primarily humanitarian, the operation also served to study the effectiveness of telemedicine as it might be used in space. Because of the high cost of space operations, the uncertainty of a rapid return to Earth of a sick or injured astronaut, and the possibility that there would not be a physician-astronaut on some missions, an advanced telemedicine system is deemed essential for future spaceflight. This is particularly important for a Mars mission of 2 to 3 years' duration during which there would be no possibility of a rapid return to Earth. With telemedicine, physicians on Earth could advise astronauts in space how to treat a sick or injured fellow astronaut.

Consequently, NASA has embarked on an ambitious telemedicine program, Spacebridge to Russia,¹⁰ to develop further its operational telemedicine capability to support the delivery of medical care in space. Because of the great expense of satellite communications, a reliable and relatively inexpensive system was developed for this project using multimedia computers and the Internet. The system links 2 sites in Moscow with 3 US clinical sites and an educational program.

Spacebridge to Russia is now in operation for clinical consultations and medical education. To date, there have been approximately 75 clinical and didactic sessions. In general, the quality of the video images has been adequate, but technological efforts are now under way to improve them. Evaluation of the usefulness of this project, including outcomes data, awaits further research after completion of necessary technological improvements.

To complement the Spacebridge audio-video system, NASA has also developed a compact telemedicine instrumentation pack (TIP) for space operations. The TIP is capable of transmitting to Earth a variety of clinical information, including vital signs, pulse oximetry, and electrocardiogram data, and video displays from oto-ophthalmoscopy.¹¹ The TIP was successfully tested onboard a space shuttle flight (STS-89) in 1998; it promises to be useful for medical consultations by emergency medical personnel at accident sites and physicians in remote areas.

NASA technology will continue to play a role in telemedicine principally through the development of miniaturization and improvements in land line and satellite communications, and by operational experience. The terrestrial use of telemedicine has not yet been incorporated by most physicians in daily practice, as evidenced by the low volume of teleconsultations.¹² The wider use of telemedicine has been somewhat dampened by controversies about quality assurance, certification, reimbursement, and liability, as well as by technological limitations.