In-Flight Cardiac Emergencies

ABSTRACT & COMMENTARY

Synopsis: In aircraft with on-board automatic external defibrillators, the ability to monitor cardiac rhythm aided decisions regarding the need for defibrillation, which was found to be unnecessary and was successfully avoided in all passengers with asystole or idioventricular rhythm.

Source: O’Rourke MF, et al. Circulation 1997;96:2849-2853.

Sudden cardiac death (scd) is defined as totally unexpected death occurring within one hour of the onset of symptoms in a victim with or without known pre-existing heart disease. SCD is clearly responsible for between 300,000 and 450,000 deaths annually in the United States, and, in fact, some authors have indicated that it is a cause for up to 20% of all natural fatalities in the industrially developed world. As many as 1000 lives are lost annually from cardiac arrest that occurs on commercial aircraft. The most common arrhythmia responsible for SCD is ventricular fibrillation, an arrhythmia that can be treated effectively only with prompt defibrillation. As in most facilities on the ground, the medical policy of almost all airlines for the treatment of in-flight cardiac arrest is to initiate and perform cardiopulmonary resuscitation pending aircraft diversion to an airport where more complete emergency services can be rendered.

O’Rourke and colleagues from the University of South Wales in Australia and the University of Manitoba in Winnipeg, Canada, reported the results of a study in which automatic external defibrillators (AEDs) were installed in major terminals and on all Qantas aircraft that flew internationally. Selected crew members were trained in the use of AEDs, and all crew members were trained in cardiopulmonary resuscitation. During a 64-month period, AEDs were used on 109 occasions, 63 times for monitoring an acutely ill patient and 46 times for an acute cardiac arrest. Twenty-seven episodes of cardiac arrest occurred in flight; 11 of these (41%) were unwitnessed, and 21 of 27 were associated with asystole or pulseless idioventricular rhythm. All 19 cardiac arrests in the airport terminals were witnessed, and ventricular fibrillation was found present in 17 (89%) of these arrests. Long-term survival from ventricular fibrillation was achieved in 26% (2 of 6 in aircraft and 4 of 17 in terminals). The authors determined that the ability to monitor cardiac rhythm aided decisions regarding the need for defibrillation, which was found to be unnecessary and was successfully avoided in all passengers with asystole or idioventricular rhythm.

COMMENT BY HAROLD L. KARPMAN, MD

Ventricular fibrillation is the most common mechanism of sudden unexpected death in western society;1,2 however, electromechanical dissociation and asystole have been found to be present in 30-50% of cardiac arrest patients. The latter causes of cardiac arrest are more common when the episodes are unwitnessed. The most important determinate of successful cardiopulmonary resuscitation is the time interval from cardiovascular collapse to initial intervention, and, since most patients are found to be in ventricular fibrillation, the time from onset to defibrillation is a key element in the acute management of the cardiac arrest victim. The chance of survival decreases 7-10% for each minute that defibrillation is delayed, and timely initiation of therapy is no less important when victims are located in airplanes than it is when they are in airport terminals or in the emergency department/coronary care unit environments. Until recently, most airlines did not even have basic medical equipment such as stethoscopes and sphygmomanometers, but, as the result of many recent studies regarding SCD have demonstrated, airline medical directors have started to turn away from the concept that a fast landing is the best overall way to treat a patient suffering from an acute cardiac arrest. Aircraft diversion is an obviously unsatisfactory alternative for patients with cardiac arrest, since, even under ideal conditions, an emergency landing from a cruising altitude will take at least 20 minutes (or longer), which makes the long-term survival rate of in-flight patients with ventricular fibrillation extremely low.

In the Qantas Airlines Cardiac Arrest Program, the AEDs functioned well, with shocks being delivered appropriately to all patients with ventricular fibrillation and to none with sinus rhythm, asystole, idioventricular rhythm, or electromechanical dissociation. Therefore, there is now little excuse for all airlines not to install monitor-defibrillator devices, especially on long overseas flights and especially since the Public Access Defibrillation initiative of the American Heart Association has resulted in the development of smaller and simpler to operate defibrillators for use by even the general public with minimal training. In addition, the cost of these units has been decreasing steadily, and therefore the cost of equipping airplanes and terminals with AEDs is no longer an obstacle. One must also consider the economic advantages of not diverting aircraft for the care of victims with SCD who 1) remain pulseless, 2) had no treatable arrhythmias, and 3) were successfully defibrillated and stabilized. In the Qantas experience, there had been no diversion for cardiac arrests caused by asystole over the previous five years, and, in the last two years of the study, there were no diversions for idioventricular rhythms. Therefore, the availability of the AEDs in flight appeared not only to permit improved management of cardiac arrest but also to have been responsible for avoiding unnecessary and futile diversions.3,4

Congressional legislation is pending that will require commercial flights to carry adequate medical supplies and equipment to deal with in-flight medical emergencies. This bill would also require airlines to carry AEDs, will require each member of the flight crew to be trained in cardiopulmonary resuscitation and in the use of the AEDs, and will also include a "good Samaritan" provision that will exempt trained airline staff, physicians, and other medical personnel who step forward to offer assistance during in-flight medical emergencies from any liability with respect to the outcome of the event. There seems to be little question that providing this relatively simple equipment and appropriate personnel training will lead to a significant improvement in airborne cardiac arrest statistics. Finally, if these changes, which were once thought to be radical in nature, can be successfully initiated in the reasonably near future, there seems to be little reason why similar equipment and personnel training cannot be provided for country clubs, major office buildings, factories, conventional centers, sports stadiums, and other venues where large public gatherings occur.

References

1. Hallstrom AP, et al. Emerg Health Serv Q 1983;1:41-49.

2. Herlitz J, et al. Br Heart J 1994;72:408-411.

3. Kellermann AL, et al. JAMA 1993;270:1433-1436.

4. Bonnin MJ, et al. JAMA 1993;270:1457-1462.

Which of the following is false? In the Qantas Airline Cardiac Arrest Program:

a. all cardiac arrests in airline terminals were unwitnessed.

b. long-term survival occurred in 33% of airborne episodes of ventricular fibrillation.

c. defibrillator shocks were not delivered to any patients with sinus rhythm, asystole, idioventricular rhythm, or electromechanical dissociation.

d. all of the above.