This study sought to assess chest compression rates (CCR) during out-of-hospital cardiac arrest (OHCA) care, comparing periods when a metronome was used to periods without one. A retrospective cohort analysis was conducted on non-traumatic OHCA incidents managed by the Seattle Fire Department between January 1, 2013, and December 31, 2019. The intervention consisted of an audio metronome set to 110 beats per minute during CPR. The principal measure was the median CCR across CPR intervals performed with versus without metronome guidance. A total of 2,132 OHCA events contributed 32,776 minutes of CPR data; 15,667 minutes (48%) occurred without metronome assistance, whereas 17,109 minutes (52%) involved metronome use. In the absence of a metronome, the median CCR was 112.8 compressions per minute (IQR 108.4–119.1), with 27% of CPR minutes falling outside the 100–120 range. Under metronome guidance, the median CCR was 110.5 per minute (IQR 110.0–112.0), and fewer than 4% of minutes deviated above 120 or below 100. Compression rates of 109, 110, or 111 occurred during 62% of metronome-guided minutes compared with 18% of minutes without metronome support. Using a metronome during CPR markedly improved adherence to a predetermined compression rate, reducing variability and promoting consistent target performance.
