['Quality cardiopulmonary resuscitation (CPR) and timely defibrillation are associated with increasing survival to hospital discharge from out-of-hospital cardiac arrest (OHCA). The objective of this study was to demonstrate that performance coaching during an OHCA would improve compression depth and time to defibrillation (TTD).', 'This study was conducted in a single emergency medical services (EMS) agency and utilized data collected from 815 patients treated between 1/1/2012 and 12/31/2013. The intervention used multiple Plan-Do-Study-Act (PDSA) cycles to train fire captains to translate performance data into active direction. Testing began in simulation with small-scale expansions prior to system-wide implementation. Performance metrics included average (reported as a percentage) and actual compression depth (reported in millimeters), and TTD (an average in seconds). Analysis was conducted using Xbar and S control charts with standard assessment of special cause for performance data. A statistical shift was seen in means and standard deviations for both depth metrics.', 'Average depth of compressions improved from 69.8% (SD=28.0%) to 80.4 (SD=21.8%). Depth of compressions delivered increased from 43.6mm (SD=8.2mm) to 47.2mm (SD=8.1mm). Analysis of the S charts indicates a statistical shift in process variation for TTD.'] Does introduction of performance coaching during cardiopulmonary resuscitation improve compression depth and time to defibrillation in out-of-hospital cardiac arrest?