Effect of metronome rates on the quality of bag-mask ventilation during metronome-guided 30:2 cardiopulmonary resuscitation: A randomized simulation study

BACKGROUND: Metronome guidance is a feasible and effective feedback technique to improve the quality of cardiopulmonary resuscitation(CPR). The rate of the metronome should be set between 100 to 120 ticks/minute and the speed of ventilation may have crucial effect on the quality of ventilation. We compared three different metronome rates(100, 110, 120 ticks/minute) to investigate its effect on the quality of ventilation during metronome-guided 30:2 CPR.METHODS: This is a prospective, randomized, crossover observational study using a Respi Trainer r. To simulate 30 chest compressions, one investigator counted from 1 to 30 in cadence with the metronome rate(1 count for every 1 tick), and the participant performed 2 consecutive ventilations immediately following the counting of 30. Thirty physicians performed 5 sets of 2 consecutive(total 10) bag-mask ventilations for each metronome rate. Participants were instructed to squeeze the bag over 2 ticks(1.0 to 1.2 seconds depending on the rate of metronome) and defl ate the bag over 2 ticks. The sequence of three different metronome rates was randomized.RESULTS: Mean tidal volume significantly decreased as the metronome rate was increased from 110 ticks/minute to 120 ticks/minute(343±84 m L vs. 294±90 m L, P=0.004). Peak airway pressure significantly increased as metronome rate increased from 100 ticks/minute to 110 ticks/minute(18.7 vs. 21.6 mm Hg, P=0.006).CONCLUSION: In metronome-guided 30:2 CPR, a higher metronome rate may adversely affect the quality of bag-mask ventilations. In cases of cardiac arrest where adequate ventilation support is necessary, 100 ticks/minute may be better than 110 or 120 ticks/minute to deliver adequate tidal volume during audio tone guided 30:2 CPR.