Background: The duration of cardiopulmonary resuscitation (CPR) is an important factor associated with the outcomes for an out-of-hospital cardiac arrest. However, the appropriate CPR duration remains unclear considering pre- and in-hospital settings. The present study aimed to evaluate the relationship between the CPR duration (including both the pre- and in-hospital duration) and neurologically favorable outcomes 1-month after cardiac arrest. Methods: Data were utilized from a prospective multi-center cohort study of out-of-hospital cardiac arrest patients transported to 67 emergency hospitals between January 2012 and March 2013 in the Kanto area of Japan. A total of 3,353 patients with out-of-hospital cardiac arrest (age ≥18years) who underwent CPR by emergency medical service personnel and achieved the return of spontaneous circulation in a pre- or in-hospital setting were analyzed. The primary outcome was a 1-month favorable neurological outcome. Logistic regression analysis was performed to estimate the influence of cardiopulmonary resuscitation duration. The CPR duration that achieved a cumulative proportion >99% of cases with a 1-month neurologically favorable outcome was determined. Results: Of the 3,353 eligible cases, pre-hospital return of spontaneous circulation was obtained in 1,692 cases (50.5%). A total of 279 (8.3%) cases had a 1-month neurologically favorable outcome. The CPR duration was significantly and inversely associated with 1-month neurologically favorable outcomes with adjustment for pre- and in-hospital confounders (adjusted odds ratio: 0.911, per minute, 95% CI: 0.892-0.929, p < 0.001). After 30min of CPR, the probability of a 1-month neurologically favorable outcome decreased from 8.3 to 0.7%. At 45min of CPR, the cumulative proportion for a 1-month neurologically favorable outcome reached >99%. Conclusions: The CPR duration was independently and inversely associated with 1-month neurologically favorable outcomes after out-of-hospital cardiac arrest. The CPR duration required to achieve return of spontaneous circulation in >99% of out-of-hospital cardiac arrest patients with a 1-month favorable neurological outcome was 45min, considering both pre- and in-hospital settings.
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