The response time threshold for predicting favourable neurological outcomes in patients with bystander-witnessed out-of-hospital cardiac arrest

ObjectiveIt is well established that the period of time between a call being made to emergency medical services (EMS) and the time at which the EMS arrive at the scene (i.e. the response time) affects survival outcomes in patients who experience out-of-hospital cardiac arrest (OHCA). However, the relationship between the response time and favourable neurological outcomes remains unclear. We therefore aimed to determine a response time threshold in patients with bystander-witnessed OHCA that is associated with positive neurological outcomes and to assess the relationship between the response time and neurological outcomes in patients with OHCA.MethodsThis study was a retrospective, observational analysis of data from 204,277 episodes of bystander-witnessed OHCA between 2006 and 2012 in Japan. We used classification and regression trees (CARTs) and receiver operating characteristic (ROC) curve analyses to determine the threshold of response time associated with favourable neurological outcomes (Cerebral Performance Category 1 or 2) 1 month after cardiac arrest.ResultsBoth CARTs and ROC analyses indicated that a threshold of 6.5 min was associated with improved neurological outcomes in all bystander-witnessed OHCA events of cardiac origin. Furthermore, bystander cardiopulmonary resuscitation (CPR) prolonged the threshold of response time by 1 min (up to 7.5 min). The adjusted odds ratio for favourable neurological outcomes in patients with OHCA who received care within ≤6.5 min was 1.935 (95% confidential interval: 1.834–2.041, P < 0.001).ConclusionsA response time of ≤6.5 min was closely associated with favourable neurological outcomes in all bystander-witnessed patients with OHCA. Bystander CPR prolonged the response time threshold by 1 min.