Abstract 270: Use of Transthoracic Impedance to Monitor the Quality of Chest Compressions in a Porcine Model of Cardiac Arrest

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Introduction. The quality of cardiopulmonary resuscitation (CPR), especially adequate compression depth, is associated with return of spontaneous circulation (ROSC) and is recommended to be measured routinely. Numerous CPR feedback techniques have been employed to monitor the quality of chest compression and demonstrated their utility in improving the effectiveness of CPR. In the current study, we investigated the relationship among transthoracic impedance (TTI) measured from the defibrillation electrodes, chest compression depth, and coronary perfusion pressure (CPP) in a porcine model of cardiac arrest. Methods. In 14 male pigs weighing between 28 to 34 kg, ventricular fibrillation (VF) was electrically induced and untreated for 6 mins. Animals were then randomized to either optimal or suboptimal chest compression group. Optimal depth of manual compression in 7 pigs was defined as a decrease of 25% in anterior posterior diameter of the chest during CPR, while suboptimal compression was defined as 70% of the optimal depth. After 2 mins of chest compression, defibrillation was attempted with a 120-J rectilinear biphasic shock. ECG, aortic pressure, right atrial pressure, compression depth, together with TTI were continuously recorded. Results. There were no differences in baseline measurements between groups. All animals had ROSC after optimal compressions, this contrasted with suboptimal compressions, after which only 2 of the animals had ROSC (100% vs. 28.57%, p = 0.021). The correlation coefficient was 0.89 between TTI amplitude and compression depth ( p < 0.001), 0.82 between TTI amplitude and CPP ( p < 0.001). Conclusion. Amplitude change of TTI was strongly correlated with chest compression depth and CPP. The TTI measured from defibrillator electrodes, therefore has the potential to serve as a reliable indicator to monitor the quality of chest compression during CPR.