Dispatcher Assistance Worsened Outcomes of Unwitnessed Out-of Hospital Cardiac Arrest: An Observational Study with Component Analysis of Rescue Breath Combination and Dispatcher Assistance

Objectives: This study aimed to analyze the effects of combinations of rescue breathing and chest compression in CPR performed by a bystander (BCPR) on the outcomes of out-of-hospital cardiac arrest (OHCA) events. Particular attention was paid to unwitnessed case by bystander. Methods: This retrospective study analyzed the prospectively collected data of 212,003 unwitnessed and 117,920 bystander-witnessed OHCA cases between 2014 and 2016 in Japan. BCPR classification was based on two clinical components: whether or not DA was provided, and whether standard CPR (with breaths) or compression-only CPR was performed. Main Outcome Measures: A neurologically favorable outcome at one month. Results: Univariate analysis showed that, in unwitnessed cases, there was no significant association between the provision of BCPR and a neurologically favorable outcome (BCPR vs. no-BCPR: 0.65% (686/106,152) vs. 0.66% (694/105,851)). In bystander-witnessed cases, the rates were 5.6% (3,538/62,814) vs. 3.5% (1,911/55,106). After classifying BCPR according to the two clinical components, the outcomes of unwitnessed cases were improved for standard BCPR with DA and compression-only, for standard BCPR wit