Abstract 63: Hands-On Defibrillation: An Analysis of Current Flow Through Rescuers In Contact With Patients During Biphasic External Defibrillation

Abstract

Background: During cardiopulmonary resuscitation, the need for rescuers to stand clear before a shock is delivered invariably interrupts chest compressions. Brief interruptions like these reduce the efficacy of defibrillation in animal models. Current flow through a rescuer in contact with a patient being shocked with modern biphasic waveforms and adhesive patch electrodes has not been investigated. We hypothesized that leakage current is low through a rescuer performing chest compressions at the time of shock delivery. Methods: During 18 elective cardioversions using truncated exponential biphasic waveforms (median energy 200 joules, range 100 –360 joules), an investigator serving as the rescuer placed a gloved hand on the patient’s anterior chest immediately adjacent to the defibrillating patch with approximately 20lbs of pressure to simulate chest compressions. Skin electrodes were used to connect the rescuer’s thigh to the patient’s posterior shoulder, simulating a worst-case return current pathway. During shock delivery, voltage and current through the rescuer (hand to thigh) were recorded using a digital storage oscilloscope during the shock delivery. Results: In no cases were shocks perceptible to the rescuer. Mean patient transthoracic impedance was 57 +/− 14 ohms (range 36 –79 ohms). Potential differences in volts (V) between the rescuer’s wrist and thigh ranged from 1.7 to 14 V (mean 6.7 +/− 2.7 V). Calculated impedances through rescuers ranged from 8,190 to 100,400 ohms (mean 30,100 +/− 20,400 ohms). The average leakage current flowing through the rescuer’s body for each phase of the shock waveform was 273 +/−191 microamperes (range 1 to 910 microamperes). All measured values in our series were well below 2,500 microamperes, an accepted safety standard for earth-leakage current in medical devices. Conclusions: Even in a simulated worst-case scenario, a rescuer performing chest compressions during biphasic external defibrillation is exposed to low levels of leakage current. Our findings demonstrate the safety and feasibility of uninterrupted chest compressions during shock delivery, which may enhance the efficacy of defibrillation and cardiocerebral perfusion.