Disposable defibrillator electrodes.

The transthoracic impedance to direct-current defibrillation discharge of the half-sinusoidal waveform was compared using recently marketed disposable defibrillator electrode pads (SAF-D-FIB and DEFIB-PADS) with electrode paste as the interfaces between the defibrillator paddle electrode and chest wall. Twenty-four mongrel dogs with an average weight of 17.3 kilograms were used. Half were shocked with the defibrillator meter setting at 100 watt-seconds (mean delivered energy, 59 watt-seconds) and half at 400 watt-seconds (mean delivered energy, 205 watt-seconds). Each animal received six shocks with both paste and one of the sets of disposable pads. The sequence of shocks was changed in alternate animals. At a meter setting of 100 watt-seconds, the mean impedance using SAF-D-FIB was 59 +/- 6 ohms compared to 46 +/- 6 ohms with paste (p less than 0.001), while that encountered with DEFIB-PADS was 57 +/- 5 ohms compared to 50 +/- 5 ohms with paste (p less than 0.01). At settings of 400 watt-seconds, the impedances encountered were also significantly higher with the disposable electrode (p less than 0.01). The output of many defibrillators in use today is inadequate for consistent defibrillation of adult patients weighing more than 50 to 80 kilograms. Since a minimal peak current per unit of body weight is required for ventricular defibrillation and since a higher transthoracic impedance results in a lower delivered peak current, one should use the paddle electrode-chest wall interface that results in the lowest impedance to defibrillator discharge. The impedance encountered with disposable electrodes is significantly higher than that encountered with electrode paste. Therefore, we do not recommend the use of these disposable electrodes for defibrillation or elective cardioversion.