Association of response time interval with neurological outcomes after out-of-hospital cardiac arrest according to bystander CPR

Background: This study intended to find out how association between response time interval (RTI) and good neurological outcome is affected by bystander CPR. We hypothesized that bystander CPR will ensure positive effect in relationship between RTI and clinical outcome. Methods: A retrospective, observational study was made with Pan-Asian Resuscitation Outcome Study data from January 2009 to December 2016. Six cities from four Asian countries were selected. EMS-treated, non-traumatic witnessed out-of-hospital cardiac arrest (OHCA) cases were included. General demographic data, prehospital cardiac arrest details and clinical outcome were collected and analyzed according to whether bystander CPR was performed. Good neurological outcome and survival discharge were primary and secondary outcomes. Results: A total of 13,245 OHCA cases were analyzed. Median EMS response time intervals were 6 min, regardless of bystander CPR. Dividing into RTI time range by 3 min, good neurological outcome and survival discharge were only significant in 3 to 6 minutes group (adjusted odds ratio [AOR] 1.42, 1.17–1.73 95% confidence interval [CI] and AOR 1.31, 1.15–1.51 95% CI) in non-bystander CPR group but in bystander CPR group significant RTI time range was 3 to 9 min (AOR 2.02, 1.82, 1.62–2.52, 1.48–2.25 95% CI for primary, AOR 1.66, 1.43, 1.41–1.96, 1.22–1.67 95% CI for secondary). Conclusions: As response time interval increased, slower deterioration of good neurological outcome and survival discharge was shown in cardiac arrest patients with bystander CPR performed. If bystander CPR is provided, RTI time range showing significant neurological outcome and survival improvement seems to be relatively lengthened.