Metronome improves compression and ventilation rates during CPR on a manikin in a randomized trial

Aim: We hypothesized that a unique tock and voice metronome could prevent both suboptimal chest compression rates and hyperventilation. Methods: A prospective, randomized, parallel design study involving 34 pairs of paid firefighter/emergency medical technicians (EMTs) performing two-rescuer CPR using a Laerdal SkillReporter Resusci Anne^® manikin with and without metronome guidance was performed. Each CPR session consisted of 2 min of 30:2 CPR with an unsecured airway, then 4 min of CPR with a secured airway (continuous compressions at 100 min^-1 with 8-10 ventilations/min), repeated after the rescuers switched roles. The metronome provided "tock" prompts for compressions, transition prompts between compressions and ventilations, and a spoken "ventilate" prompt. Results: During CPR with a bag/valve/mask the target compression rate of 90-110 min^-1 was achieved in 5/34 CPR sessions (15%) for the control group and 34/34 sessions (100%) for the metronome group (p < 0.001). An excessive ventilation rate was not observed in either the metronome or control group during CPR with a bag/valve/mask. During CPR with a bag/endotracheal tube, the target of both a compression rate of 90-110 min^-1 and a ventilation rate of 8-11 min^-1 was achieved in 3/34 CPR sessions (9%) for the control group and 33/34 sessions (97%) for the metronome group (p < 0.001). Metronome use with the secured airway scenario significantly decreased the incidence of over-ventilation (11/34 EMT pairs vs. 0/34 EMT pairs; p < 0.001). Conclusions: A unique combination tock and voice prompting metronome was effective at directing correct chest compression and ventilation rates both before and after intubation.