An investigation into the use of the impedance cardiogram as a predictor of manual chest compression efficacy

High quality chest compressions (CCs) have been proven to increase patient survival, during cardiac arrest. The impedance cardiogram (ICG) may provide a simple and non-invasive CPR coaching system to improve CC efficacy of minimally trained users. Cardiac arrest was induced in eleven swine. Manual CCs were applied at a fixed depth for two-minute episodes, increasing for each successive episode. Physiological data was recorded at 30s intervals. The primary analysis assessed the relationship between ICG amplitude and CC depth using a 5s analysis window. The secondary analysis compared the ICG amplitude against captured physiological data and CC depth, using a 30s window. The primary analysis yielded a strong Pearson correlation coefficient (95% confidence interval) of 0.90 (0.89, 0.91) between ICG amplitude and CC depth. The secondary analysis produced an overall correlation of 0.92 (0.90, 0.94) between ICG amplitude and CC depth. The within-animal correlation for ICG amplitude and both end-tidal carbon dioxide and systolic blood pressure was 0.94 (0.93, 0.95) and 0.90 (0.88, 0.92) respectively. Our data suggests that the amplitude of ICG is a good predictor of CC efficacy in a porcine model of cardiac arrest, when manual CCs are applied.