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 without DA, but not for compression-only BCPR with DA. Multivariate logistic regression analysis focusing on the two clinical components in unwitnessed BCPR cases showed worse neurologically favorable outcomes with DA provision but better outcomes for standard BCPR, without significant interaction. In bystanderwitnessed cases, DA provision was associated with better outcomes, with significant interaction. Conclusions: Compared with no-BCPR, compression-only BCPR with DA does not improve neurologically favorable outcomes. Standard BCPR without DA resulted in the best outcomes in unwitnessed OHCA cases.