No abstract

Background : The recent recommendation for hands-only (continuous chest compression) CPR has caused concern that professional rescuers may over-ventilate to compensate for a lack of ventilation before their arrival. Previous research shows that over-ventilation can be deleterious. Methods : We conducted a prospective, randomized, parallel design study of the effectiveness of a customized metronome to guide both compressions and ventilations during CPR with an unsecured airway or a secured airway. Firefighter EMTs performed 2-rescuer CPR on an instrumented manikin, 34 EMTs with and 34 EMTs without metronome guidance. Each session consisted of 2 min of 30:2 CPR with an unsecured airway, then 4 min of CPR with a secured airway (100/min continuous compressions and 8 –10 ventilations/min), repeated after the rescuers switched roles. The metronome gave “tock” prompts for compressions and a spoken “ventilate” prompt. Endpoints included compression and ventilation rates. Results : Metronome use significantly decreased the incidence of over-ventilation (11/34 CPR sessions vs 0/34; p<0.001). As previously documented, compression rate errors were significantly less with the metronome. For unsecured airways, mean compression rate error was 21/min for control vs. 0 for the metronome group, (p<0.001); for secured airways, mean compression rate error was 18/min for control vs. 1/min for the metronome group (p<0.001). Conclusions : A compression/ventilation metronome helps avoid over-ventilation and improves compression rate when used by professional rescuers on a manikin. The metronome may be highly effective in avoiding over-ventilation during CPR with a secured airway.