Association of Dispatcher-assisted, Chest Compression-only Resuscitation With Annual Increases in Survival From Unwitnessed Out-of-hospital Cardiac Arrests

Abstract Background: Many out-of-hospital cardiac arrest cases are unwitnessed. For both unwitnessed and witnessed cases, recent guidelines endorse the dispatcher’s instruction of compression-only cardiopulmonary resuscitation to lay rescuers without previous resuscitation training. This study aimed to investigate the changes in the composition of bystander resuscitation based on the combination of rescue breathing and dispatcher-assisted resuscitation, and the association of the changes in bystander resuscitation content with annual outcome improvement in unwitnessed out-of-hospital cardiac arrest cases.Method: Retrospective analysis of prospective national cohort study in a population-based setting. Out-of-hospital cardiac arrest cases in 2009–2016 (986,760 cases) were reviewed to provide a complete dataset for analyses (941,858 cases). Main outcome was neurologically favorable survival at 1 month.Results: Of the 941,858 cases, the rates of neurologically favorable survival adjusted for prehospital confounders continuously increased annually. When classified into 5 groups according to the contents of resuscitation, the proportions of the dispatcher-assisted compression-only resuscitation group increased annually, whereas the proportions of the other groups decreased. That is, the shift from standard (defined as the combination of chest compressions and rescue breathings) to compression-only bystander resuscitation were observed for both unwitnessed and bystander-witnessed cases. In unwitnessed cases, the survival rate of the dispatcher-assisted compression-only resuscitation group was always lower than that of the no-resuscitation group during the study period. On the other hand, the survival rate of dispatcher-assisted standard resuscitation group exceeded that of the no-resuscitation group at the end of the study period (adjusted odds ratio; 95% confidence intervals (CI), 1.41; 1.02–1.93), and the increase in survival rate was prominent compared to that of the dispatcher-assisted compression-only resuscitation group (adjusted unit odds ratio/year; 95% CI, 1.15; 1.08–1.24 vs. 1.04; 1.00–1.07).Conclusions: The proportions of dispatcher-assisted compression-only resuscitation group increased annually, but its survival rate of the neurologically favorable 1-month did not exceed compared to that of the no-resuscitation group in unwitnessed cases. The dispatcher-assisted compression-only resuscitation did not appear to be an ideal management for unwitnessed out-of-hospital cardiac arrest cases.