Address for Correspondence:

2 Background—Minimizing pauses in chest compressions during cardiopulmonary resuscitation (CPR) is a focus of current Guidelines. Prior analyses found that prolonged pauses for defibrillation (peri-shock pauses) are associated with worse survival. We analyzed resuscitations to characterize the association between pauses for all reasons and both ventricular fibrillation termination and patient survival. Methods and Results—In 319 patients with ventricular tachycardia/fibrillation out-of-hospital cardiac arrest, we analyzed recordings from all defibrillators used during resuscitation and measured durations of all CPR pauses. Median (25th, 75th percentile) durations in seconds were 32 (22, 52) for the longest pause for any reason, 23 (14, 34) for the longest peri-shock pause, and 24 (11, 38) for the longest non-shock pause. Multivariable regression models showed lower odds for survival per five second increase of the longest overall pause (OR 0.89, 95%CI 0.83-0.95), longest peri-shock pause (OR 0.85, 95%CI 0.77-0.93), and longest non-shock pause (OR 0.83, 95%CI 0.75-0.91). In 36 % of cases, the longest pause was a non-shock pause; this subgroup ha