Abstract 54: The Impedance Cardiogram as an Indicator of Chest Compression Efficacy During Cardiopulmonary Resuscitation in a Porcine Model: Correlation with Physiological Parameters and Comparison with Compression Depth and Thrust

Abstract

Introduction The 2010 AHA resuscitation guidelines re-emphasised the importance of chest compressions as the cornerstone of effective CPR. In an attempt to improve chest compression efficacy numerous CPR feedback devices have been developed and have demonstrated their utility in improving guideline compliant CPR but not patient outcomes. The impedance cardiogram (ICG) provides a non-invasive measure of haemodynamic status and has been investigated as an additional method of improving CPR. Objectives The purpose of this study was to examine the relationship between chest compression thrust, depth and ICG amplitude during CPR and establish their correlation with invasive physiological measurements. Materials and methods Ethical approval for this study was granted by the Northern Ireland Home Office. A total of 12 porcine models were used weighing mean 31kg. Anaesthesia was achieved with intravenous propofol and inhaled isoflourane. Ventricular fibrillation was induced using a pacing wire inserted into the right ventricle. CPR was administered using the HLR-201®, Michigan Instruments. The Impedance Cardiogram (ICG) was recorded via 2 standard defibrillation electrodes. Depth (cm), thrust (kg), end-tidal CO 2 (kPa), systolic blood pressure (mmHg), carotid flow (ml/min) and cardiac output (L/min) were measured at 2 minute intervals for each model. Results There is a strong correlation between ICG amplitude and physiological parameters, comparable to correlations achieved with compression depth and thrust. (Table 1) Table 1: Summary of correlations between physiological parameters and ICG, compression depth and thrust during CPR Conclusions The ICG amplitude provides an additional measurement of CPR efficacy with physiological correlations comparable to both chest compression thrust and depth. This non-invasive measurement could be exploited in the development of new CPR feedback algorithms for automated external defibrillators.