Transthoracic impedance variability to assess quality of chest compression in out-of-hospital cardiac arrest.

Abstract

Chest compression is a lifesaving intervention in out-of-hospital cardiac arrest (OHCA), but the optimal metrics to assess its quality have yet to be identified. The objective of this study was to investigate whether a new parameter, that is, the variability of the chest compression-generated transthoracic impedance (TTI), namely Imp_CC , which measures the consistency of the chest compression maneuver, relates to resuscitation outcome. This multicenter observational, retrospective study included OHCAs with shockable rhythm. Imp_CC variability was evaluated with the power spectral density analysis of the TTI. Multivariate regression model was used to examine the impact of Imp_CC variability on defibrillation success. Secondary outcome measures were return of spontaneous circulation and survival. Among 835 treated OHCAs, 680 met inclusion criteria and 565 matched long-term outcomes. Imp_CC was significantly higher in patients with unsuccessful defibrillation compared to those with successful defibrillation (p = .0002). Lower Imp_CC variability was associated with successful defibrillation with an odds ratio (OR) of 0.993 (95% confidence interval [95% CI], 0.989-0.998, p = .003), while the standard chest compression fraction (CCF) was not associated (OR 1.008 [95 % CI, 0.992-1.026, p = .33]). Neither Imp_CC nor CCF was associated with long-term outcomes. In this population, consistency of chest compression maneuver, measured by variability in TTI, was an independent predictor of defibrillation outcome. Imp_CC may be a useful novel metrics for improving quality of care in OHCA.