Associations Between Perfusion Index During Out-Of-Hospital Cardiopulmonary Resuscitation, Cardiopulmonary Resuscitation Quality and Return Of Spontaneous Circulation.

BACKGROUND: The association between perfusion index (PI) and out-of-hospital cardiac arrest survival outcomes is unknown. The American Heart Association suggested the need to improve the monitoring of cardiopulmonary resuscitation and chest compression quality. We hypothesized that higher event-average perfusion index values are associated with higher probability of return of spontaneous circulation, better survival and neurological outcomes. METHODS: In this prospective cohort study of index out-of-hospital cardiac arrests attended from January 2022 through October 2024, we analyzed the association of the event-average perfusion index value with sustained return of spontaneous circulation. Secondary exposures included survival to hospital admission, favorable neurological outcome (Cerebral Performance Category ?3 or no change from baseline) and associations between epoch-average PI and CPR quality metrics. RESULTS: We included 98 index out-of-hospital cardiac arrests (mean [Standard Deviation]) age 62.1 years [17.6], 32% female, 9.2% shockable rhythm. Median event-average perfusion index was 0.29 ([Q1, Q3], 0.11, 0.92). Events with sustained return of spontaneous circulation had a higher event-level average perfusion index (0.92 [0.44, 1.73] mmol/L versus 0.19 [0.09, 0.55]; P<0.001). The receiver operating characteristic analyses of PI, as a predictor of sustained return of spontaneous circulation, identified an area under the curve of 0.77 [95% CI, 0.68?0.86]) with an optimal cut point at 0.61 (sensitivity 0.67, specificity 0.81). After adjusting for confounders, PI was associated with higher relative risk of sustained ROSC (adjusted odds ratio, 2.6 [95% CI, 1.3?5.1]; P<0.001). Event-average PI was also associated with higher relative risk of survival to hospital admission (adjusted odds ratio, 2.1 [95% CI, 1.2?3.7]; P=0.001) while it was not associated with higher relative risk of neurological intact survival (adjusted odds ratio, 4.0 [95% CI, 0.8?19.4]; P=0.085). Higher epoch-average PI was independently associated with higher chest compression fraction (P=0.003). CONCLUSIONS: Higher event-average PI was associated with higher probability of sustained return of spontaneous circulation. Event-average PI was associated with higher adjusted probability of return of spontaneous circulation, but not with neurological intact survival. Epoch-average PI was positively correlated with chest compression fraction.