Brief Report
A higher chest compression rate may be necessary for metronome-guided cardiopulmonary resuscitation

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Abstract

Objectives

Metronome guidance is a simple and economical feedback system for guiding cardiopulmonary resuscitation (CPR). However, a recent study showed that metronome guidance reduced the depth of chest compression. The results of previous studies suggest that a higher chest compression rate is associated with a better CPR outcome as compared with a lower chest compression rate, irrespective of metronome use. Based on this finding, we hypothesized that a lower chest compression rate promotes a reduction in chest compression depth in the recent study rather than metronome use itself.

Methods

One minute of chest compression–only CPR was performed following the metronome sound played at 1 of 4 different rates: 80, 100, 120, and 140 ticks/min. Average compression depths (ACDs) and duty cycles were compared using repeated measures analysis of variance, and the values in the absence and presence of metronome guidance were compared.

Results

Both the ACD and duty cycle increased when the metronome rate increased (P = .017, <.001). Average compression depths for the CPR procedures following the metronome rates of 80 and 100 ticks/min were significantly lower than those for the procedures without metronome guidance.

Conclusions

The ACD and duty cyle for chest compression increase as the metronome rate increases during metronome-guided CPR. A higher rate of chest compression is necessary for metronome-guided CPR to prevent suboptimal quality of chest compression.

Introduction

The quality of cardiopulmonary resuscitation (CPR) is a very important prognostic factor for cardiac arrest [1], [2], [3]. Many trials have been executed to improve the quality of CPR using various feedback devices [4], [5], [6], [7], [8], [9], [10], [11], [12], [13]. Metronome guidance is a very cost-effective and feasible method relative to other feedback techniques. In addition, metronome guidance has been shown to improve the outcome of CPR [4], [5], [6]. Its ability to regulate the compression rate and ventilation has also been confirmed by multiple studies [4], [5], [6], [13], [14], [15]. Furthermore, one study demonstrated that hyperventilation during CPR could be prevented by metronome guidance [13]. However, negative effects of this method have also been reported; one study reported that metronome guidance reduced the average depth of chest compression, which is an important quality factor for CPR [14]. Metronome-guided CPR may need to be discouraged if the negative effect on the depth of chest compression cannot be avoided because a sufficient depth is one of the most important factors affecting survival after CPR [16], [17].

Oh et al [14] suggested that the reduction in the average chest compression depth (ACD) may be caused by the multitasking required by the simultaneous use of auditory perception and CPR technique. However, the exact cause of this reduction has not yet been elucidated. It is important to identify the cause to prevent the possible negative impact of metronome guidance on CPR.

There is a consistent finding among studies that evaluated the effect of metronome guidance on CPR; a higher chest compression rate was associated with a better CPR outcome than a lower chest compression rate, irrespective of metronome use [4], [5], [6], [14]. However, there has been no study focusing on the effect of the metronome rate on metronome-guided CPR. Hence, we performed this study to evaluate whether the metronome rate affects the quality of closed chest compression during metronome-guided CPR.

Section snippets

Study design

This study was approved by our institutional review board. This was a prospective, randomized, cross-over trial involving simulated 1 person CPRs.

Participants

Senior medical students from our institution who had finished their 2 mandatory CPR training courses, which were based on the American Heart Association basic life support course according to the 2005 American Heart Association guidelines for CPR and emergency cardiovascular care [18], within 1 year were enrolled in this study. Students who had a

Results

A total of 27 senior medical students participated in the study. The mean age of the participants was 24 ± 2 years, and there were 9 female participants (33%). The ACD significantly increased as the metronome rate increased (P = .017), following a linear trend (P < .001) (Fig. 1A). Duty cycle also significantly increased as the metronome rate increased (P < .001), also following a linear trend (P < .001) (Fig. 1B). Fractions of inaccurate hand positions and incomplete releases were not

Discussions

This is the first study to specifically evaluate the effect of the rate of metronome on the quality of CPR. Our results suggest that metronome guidance lowers the ACD when it occurs at a rate of 100 ticks/min, which is the current recommended chest compression rate. In fact, a rate higher than this is necessary to avoid lowering the ACD, which will ultimately lead to suboptimal chest compression.

This study was based on the previous study by Oh et al [14], which demonstrated that

Conclusions

The average depth and duty cycle of chest compression increase as the metronome rate increases during metronome-guided CPR. The average depth of chest compression is significantly lower in metronome-guided CPR with the rate set equal to or below the rate recommended by the guidelines (100 ticks/min). A higher rate of chest compression is necessary during metronome-guided CPR to prevent the suboptimal quality of chest compression.

Cited by (18)

  • Retraining basic life support skills using video, voice feedback or both: A randomised controlled trial

    2013, Resuscitation
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    Jäntti et al. reported earlier that metronome guidance used when performing CPR, helped to correct chest compression rate in experienced rescuers, but did not affect chest compression depth or rescuer fatigue.26 Chung et al. observed that the average compression depth was significantly lower in metronome-guided CPR with the rate set at 100/min.27 A similar observation was made in the current study where metronome-guided practice-while-watching was not associated with improvement in compression depth.

  • Excessive chest compression rate is associated with insufficient compression depth in prehospital cardiac arrest

    2012, Resuscitation
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    On the other hand, the defibrillator activated a metronome at 100/min when compression rate was <80/min. Manikin studies have shown that a metronome not only guides compression rate but can also increase or decrease compression depth.9,16–19 Chung and colleagues reported that an increase in rate also increased compression depth in a manikin study. 17

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