Transthoracic impedance to defibrillator discharge. Effect of electrode size and electrode-chest wall interface

Summary Transthoracic impedance of man to direct current defibrillator discharge has been reported to vary from 27 to 110 ohms. This study was designed to determine the effect of paddle electrode size and paddle electrode-chest wall interface on transthoracic impedance. Paddle electrode diameters studied were 4.5, 8.0, and 12.8 cm. There was a progressive decrease in impedance with increasing paddle electrode size. Paddle electrode-chest wall interfaces used were none, electrode cream, saline-soaked gauze pads, and electrode paste. The transthoracic impedance was progressively decreased with these interfaces regardless of paddle electrode size. This study suggests that when using direct current defibrillators or cardioverters, large paddle electrodes should be used with electrode paste as interface to accomplish maximum reduction in transthoracic impedance.