Release velocity ImprovemenT with a new Metronome guIding chest COmpressions: the RITMICO study

Background and trial design Outcomes of out-of-hospital cardiac arrest vary significantly, often due to the quality of cardiopulmonary resuscitation (CPR) provided. Automated real-time feedback devices have been explored to enhance CPR skills, but few devices currently ensure proper chest recoil. This study aimed to assess whether a double-click metronome could improve chest compressions (CC) metrics and particularly CC release velocity (CCRV) during CPR manikin simulation. Methods We developed and tested a double-click metronome for CPR, where the first click signals the compression and the second click marks the end of chest release. We performed a multicenter non-blinded, randomized, controlled trial including volunteers with different levels of CPR expertise. Three CC metrics—depth, rate, and CCRV—were measured using an automated external defibrillator equipped with pads for CPR quality analysis. Results 503 volunteers participated in the study, with 54% being male and a mean age of 34±12 years. The median CCRV and CC depth achieved with the double-click metronome were significantly higher compared to the standard metronome (median difference 6 mm/s, IQR-15.2, 28.5, +1.5%, p < 0.001; median difference 0.1 cm, +2.5%, IQR -0.1, 0.4, p < 0.001). The double-click metronome led to significant improvements in CC depth and CCRV across all volunteer categories, with the greater effect observed in first responders and in non-specialized healthcare personnel. Conclusions Compared to a standard metronome, the double-click metronome significantly enhances CPR quality. If further validated in real resuscitations, this new audio prompt could be a valuable tool for integration into devices designed for out-of-hospital cardiac arrest resuscitation, as well as a training tool to improve CPR quality.