The CPR compression matrix: relationship among depth, recoil, and rate

The composition of chest compressions during cardiopulmonary resuscitation (CPR) can influence the likelihood of survival. Yet, little is known about how depth, recoil, and rate simultaneously relate to one another.

We conducted a retrospective cohort study of adult cardiac arrest treated by professional rescuers in two emergency medical services (EMS) systems between 2017 and 2021. Chest compression characteristics were assessed using an accelerometer "puck". The puck assessed compression depth in millimeters (mm). Recoil was assessed by determining the residual force during compression release. We determined how depth and recoil simultaneously distribute according to rate (compression/min) for each 30-s CPR period by creating categorical groups for depth (≥50 versus <50 mm) and recoil ("complete" corresponding to no residual force and "incomplete" corresponding to any residual force at the end of decompression). We used hierarchical modeling to account for clustering to determine "optimal" compression performance (defined as ≥50 mm and complete recoil) according to rate groups.

Among 611 patients providing 27,438 discrete 30-s segments, the median compression rate was 113 (IQR 109,118), median depth was 50 mm (43,56), and 42% of segments had complete recoil. After accounting for clustering, "optimal" compression was achieved in 24% of the 100-104 rate group. This proportion declined progressively as compression rates became slower (95-99: 21%, <95: 18%) and especially as rates became faster (105-109: 20%, 110-14: 16%, 115-119: 11%, 120-124: 6%, and ≥125: 3%).

A compression rate of 100-104 per minute was associated with the greatest likelihood of simultaneously achieving optimal depth and recoil.