Excessive chest compression rate is associated with insufficient compression depth in out-of-hospital cardic arrest

Background and goal of study: In the latest Consensus on Science and Treatment Recommendations on Cardiopulmonary Resuscitation (ref), the relationship between compression rate and compression depth is considered to be a knowledge gap. In order to characterize this relationship, we performed an observational study in pre-hospital cardiac arrest patients. Materials and methods : In patients undergoing out-of-hospital cardiopulmonary resuscitation by health care professionals, chest compression rate and depth were recorded using an accelerometer (E-series monitor-defibrillator, Zoll, USA). The monitor provided real-time corrective feedback for compression rates <80/min and for depth <4 cm. Compression depth was analyzed for rates <80/min, 80-120/min and >120/min. A difference in compression depth ≥5 mm was considered potentially clinically significant. Results and discussion : Thirty-one consecutive patients were analyzed (50375 compressions, on average 1625 per patient). Of all compressions 2% were <80/min, 63% between 80-120/min and 35% >120/min. Mean compression depth for rates 80-120/min was 4.5 cm (SD=1) compared to 3.5 cm (SD=1) for compressions >120/min (P<0.001; see Figure). In 20 out of 31 (64%) patients a statistically significant lower depth was observed for rates >120/min compared to rates 80-120/min, in 10 out of 31 (32%) this difference was also clinically significant. There was no difference between the mean depth of compressions <80/min and the mean depth of compressions 80-120/min. Conclusions : Compression rates >120/min were associated with a lower compression depth. The observation that compression depth is lower with increased compression rates underscores the importance of feedback on rate during CPR. Reference Nolan JP, Hazinski MF, Billi JE, Boettiger BW, et al. Executive Summary 2010 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. Resuscitation 2010; 81S: e1-e25.

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