Abstract
Introduction: The ventricular fibrillation (VF) electrocardiogram (ECG) waveform is known to deteriorate over time if untreated, recover with CPR, and to predict defibrillation success. VF ECG measures could inform CPR quality feedback algorithms based on patient physiologic response. Objectives: Investigate the effects of chest compression parameters (rate, depth and duty cycle (DC)) on VF ECG waveform characteristics in a swine cardiac arrest model. Methods: Twelve mixed-breed domestic swine were sedated, anesthetized and paralyzed, followed by endotracheal intubation and mechanical ventilation. Animals were instrumented with a battery of physiological sensors, including multi-lead ECG, recorded continuously with a high-fidelity data acquisition unit at 1000Hz. VF was induced with a 3-second 100mA transthoracic shock. After 7 minutes, animals were randomized to receive continuous CPR with a custom robotic device using 1 of 6 pre-programmed, cross-over 2-phase CPR schemes that varied 1 parameter in 5 x 1-minute intervals per phase while holding the other 2 parameters fixed. Frequency (AMSA) and slope-based (MS) quantitative ECG characteristics of the ECG were calculated at the end of each 1-minute interval and compared between rate, depth and DC schemes, as well as experimental phases. Correlations between CPR parameter settings and ECG characteristics were calculated. Results: Compression rate showed a low-to-moderate correlation (0.454) with change in MS in Phase I, however neither DC nor depth showed a correlation with either AMSA or MS. In ANOVA models, MS differed between CPR groups at the end of Phase I (p = 0.046) but not AMSA, suggesting similar response of quantitative ECG measures after extended time intervals. Conclusions: In this study only chest compression rate in early phase CPR appeared to be related to quantitative characteristics of the VF ECG. Rate may be important clinically in the early phase of CPR.
Published Version
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