Letter by Sullivan Regarding Article, “Hands-On Defibrillation: An Analysis of Electrical Current Flow Through Rescuers in Direct Contact With Patients During Biphasic External Defibrillation”
To the Editor:
As an engineer and scientist for a leading manufacturer of external defibrillators, I feel compelled to comment on the recent report by Lloyd et al, “Hands-On Defibrillation: An Analysis of Electrical Current Flow Through Rescuers in Direct Contact With Patients During Biphasic External Defibrillation.”1 The authors of this study have the laudable goal of improving patient care by eliminating the hands-off period during a shock. However, although their results are interesting, their study has insufficient power to conclude that “uninterrupted manual chest compressions during shock delivery are feasible” (p 2513).
This study demonstrates the fact that polyethylene gloves, in the absence of electric breakdown, exhibit an extremely high insulation resistance. However, these gloves, and medical examination gloves in general, are designed as a barrier to bodily fluids, not as a reliable barrier to high-voltage electricity. As such, their electric performance may be inconsistent. Although it appears that no electric breakdown occurred in the study by Lloyd et al, they delivered only 8 maximum-voltage biphasic shocks and did not measure the voltage across the gloves themselves. Thus, their study gives little insight into the critical question of glove reliability.
In an earlier study, Tucker and Ferguson2 evaluated the electric characteristics of gloves during electrosurgery and found that 11 of the 15 gloves they tested experienced electric breakdown between 2200 and 2600 V. Had a larger sample been tested, it is reasonable to assume that lower breakdown voltages may have been found.
Biphasic defibrillators provide output voltages of up to ≈2200 V, and monophasic output voltages can be as high as 5000 V. It is unknown what fraction of that voltage is likely to appear across a caregiver during cardiopulmonary resuscitation. However, until more data are gathered, caution is prudent.
Approximately 60 000 ventricular fibrillation cardiac arrest cases occur in the United States annually,3,4 necessitating, presumably, at least that many defibrillation attempts. Given such a high usage rate, a very high glove reliability would be required to ensure rescuer safety.
A thorough study of glove reliability would include a statistical analysis to estimate the quantity of glove failures that would occur at defibrillation voltages given the current usage rate. Such a study could conceivably be undertaken if the glove breakdown voltage exceeded the defibrillation voltage by a substantial margin. Unfortunately, the data from Tucker and Ferguson suggest that this margin may not exist.
It is important for readers to understand that, in the absence of gloves or if an electric breakdown of gloves occurs during hands-on defibrillation, multiple amperes of current could flow through the caregiver. This is a serious safety hazard.
Maybe someday glove manufacturers will produce defibrillation-rated gloves. Such gloves would be designed from the start to withstand the full output voltage of an external defibrillator. Until that day, it is my recommendation that caregivers heed the “Stand clear!” warning before shocking a patient.
J.L. Sullivan is an employee of Physio-Control, Inc, a manufacturer of external defibrillators.