Abstract 264: The Association of Chest Compression Fraction and Clinical Outcomes from Shockable Out-of-Hospital Cardiac Arrest During the Resuscitation Outcomes Consortium Primed Trial

Abstract

INTRODUCTION: The role of chest compression fraction (CCF) in resuscitation of shockable out-of-hospital cardiac arrest (OHCA) is uncertain. We evaluated the relationship between CCF and clinical outcomes in a secondary analysis of the Resuscitation Outcomes Consortium (ROC) PRIMED trial. METHODS: We included OHCA patients from the ROC PRIMED trial who suffered cardiac arrest prior to EMS arrival, presented with a shockable rhythm, and had cardiopulmonary resuscitation (CPR) process data for at least one shock. We used multivariable logistic regression adjusting for Utstein variables, CPR metrics of compression rate and perishock pause, and ROC site to determine the relationship between CCF and survival to hospital discharge, return of spontaneous circulation (ROSC), and neurologically intact survival defined with Modified Rankin Score (MRS) ≤ 3. Due to potential confounding between CCF and cases that achieved early ROSC, we also performed an analysis restricted to patients without ROSC in the first 10 minutes of EMS resuscitation. RESULTS: Among the 2,558 eligible patients, median (IQR) age was 65 (54, 76) years, 76.9% were male, and mean (SD) CCF was 0.70 (0.15). Compared to the reference group (CCF < 0.60), the odds ratio (OR) for survival was 0.57 (95%CI: 0.42, 0.78) for CCF 0.60-0.79 and 0.32 (95%CI: 0.22, 0.48) for CCF ≥0.80. Results were similar for outcomes of ROSC and neurologically intact survival. Conversely, when restricted to the cohort who did not achieve ROSC during the first 10 minutes (n=1,660), the relationship between CCF and survival was no longer significant. Compared to the reference group (CCF < 0.60), the OR for survival was 0.85 (95 %CI: 0.58, 1.26) for CCF 0.60-0.79 and OR 0.87 (95%CI: 0.58, 1.36) for CCF ≥0.80. CONCLUSIONS: In this observational cohort study of OHCA patients presenting in a shockable rhythm, CCF when adjusted for Utstein predictors, CPR metrics and ROC site was paradoxically associated with lower odds of survival. The relationship between CCF and clinical outcomes was null in a sensitivity analysis restricted to patients without ROSC in the first 10 minutes. CCF is a complex measure and taken by itself may not be a consistent predictor of clinical outcome.