Ventricular fibrillation waveform properties influenced by thoracic impedance guided chest compressions in a porcine model

•Ventricular fibrillation waveform measures represent the metabolic state of the myocardium.•Thoracic impedance measurements can characterise the quality of chest compressions within a subject.•Chest compressions guided by thoracic impedance had a direct effect on ventricular fibrillation waveform properties.•Changes in VF properties due to increasing TI amplitude were reflected in return of spontaneous circulation but not shock success. Quantitative measures extracted from ventricular fibrillation (VF) waveform reflect the metabolic state of the myocardium and are associated with survival outcome. The quality of delivered chest compressions during cardiopulmonary resuscitation are also linked with survival. The aim of this research is to explore the viability and effectiveness of a thoracic impedance (TI) based chest compression (CC) guidance system to control CC depth within individual subjects and influence VF waveform properties. This porcine investigation includes an analysis of two protocols. CC were delivered in 2 min episodes at a constant rate of 110 CC min−1. Subject-specific CC depth was controlled using a TI-thresholding system where CC were performed according to the amplitude (ZRMS, 0.125 to 1.250 Ω) of a band-passed TI signal (ZCC). Protocol A was a retrospective analysis of a 12-porcine study to characterise the response of two VF waveform metrics: amplitude spectrum area (AMSA) and mean slope (MS), to varying CC quality. Protocol B was a prospective 12-porcine study to determine if changes in VF waveform metrics, due to CC quality, were associated with defibrillation outcome. Protocol A: A directly proportional relationship was observed between ZRMS and CC depth applied within each subject (r = 0.90; p