Effects of Supporting Systems During Cardiopulmonary Resuscitation: a Prospective Simulation Study to Evaluate Metronome and Real-Time Feedback

Chest compression is an essential component of cardiopulmonary resuscitation (CPR), and influences survival of cardiac arrest victims. Adherence to guideline and chest compression quality differ widely. The medical industry as well as software engineers has developed technical support (e.g. metronome and real-time feedback) to improve chest compression quality. However, which elements of real-time feedback devices best assist rescuers remain unclear. We hypothesized that only a combination of metronome and audio-visual real-time feedback and not a stand-alone metronome improves chest compression quality. In this prospective manikin study, 100 emergency medical technicians were randomly assigned to 50 teams and performed CPR in three simulated cardiac arrest scenarios. Scenario A without any technical support during CPR was the control situation. In scenario B, there was support from a stand-alone metronome (100/min). In scenario C, the team was supported by a metronome (100/min) and audio-visual real-time feedback on chest compression depth. Endpoints in each 10-minute simulation were chest compression rate, correct chest compressions (defined as correct hand position, depth, recoil in a minimum of 70%), mean ventilation rate and tidal volume. There were differences in the mean compression rate (Scenario A 118 +/- 14cc/min; Scenario B 101 +/- 4cc/min; Scenario C 101 +/- 2cc/min; B and C vs. A; p<0.05) as well as in correct chest compression (A 40% correct; B 38% correct; C 92% correct compressions; A and B vs. C, P<0.05). We found no differences in ventilation. As in previous studies, in the CPR scenarios without any technical support, chest compressions were carried out too fast and were too shallow compared with the guidelines. A stand-alone metronome improved chest compression rate but diminished chest compression depth significantly. The combination of a metronome and audio-visual feedback improved both chest compression rate and depth. A feedback-system has to take human abilities of signal perception and processing into account. A metronome can distract the rescuer from other quality characteristics of chest compressions. This study supports a combination of a metronome with a chest compression depth measurement for real-time support during CPR. More research is needed on human-machine interface for the design of feedback systems in resuscitation.