Manual Cardiopulmonary Resuscitation Versus CPR Including a Mechanical Chest Compression Device in Out-of-Hospital Cardiac Arrest: A Comprehensive Meta-analysis From Randomized and Observational Studies

Study objective

Mechanical chest compression devices have been developed to facilitate continuous delivery of high-quality cardiopulmonary resuscitation (CPR). Despite promising hemodynamic data, evidence on clinical outcomes remains inconclusive. With the completion of 3 randomized controlled trials, we conduct a meta-analysis on the effect of in-field mechanical versus manual CPR on clinical outcomes after out-of-hospital cardiac arrest.

Methods

With a systematic search (PubMed, Web of Science, EMBASE, and the Cochrane Libraries), we identified all eligible studies (randomized controlled trials and nonrandomized studies) that compared a CPR strategy including an automated mechanical chest compression device with a strategy of manual CPR only. Outcome variables were survival to hospital admission, survival to discharge, and favorable neurologic outcome.

Results

Twenty studies (n=21,363) were analyzed: 5 randomized controlled trials and 15 nonrandomized studies, pooled separately. For survival to admission, the pooled estimate of the randomized controlled trials did not indicate a difference (odds ratio 0.94; 95% confidence interval 0.84 to 1.05; P=.24) between mechanical and manual CPR. In contrast, meta-analysis of nonrandomized studies demonstrated a benefit in favor of mechanical CPR (odds ratio 1.42; 95% confidence interval 1.21 to 1.67; P<.001). No interaction was found between the endorsed CPR guidelines (2000 versus 2005) and the CPR strategy (P=.27). Survival to discharge and neurologic outcome did not differ between strategies.

Conclusion

Although there are lower-quality, observational data that suggest that mechanical CPR used at the rescuer’s discretion could improve survival to hospital admission, the cumulative high-quality randomized evidence does not support a routine strategy of mechanical CPR to improve survival or neurologic outcome. These findings are irrespective of the endorsed CPR guidelines during the study periods.

Introduction

Out-of-hospital cardiac arrests occur frequently, with an estimated incidence of 50 to 100 per 100,000 person-years.1, 2 Survival to hospital discharge ranges between 5% and 20%.¹ Both in the out-of-hospital and inhospital setting, several initiatives have been developed to improve outcome. In addition to the implementation of early access to automated external defibrillators and the initiative of dispatcher-assisted cardiopulmonary resuscitation (CPR) with chest compressions only, the introduction of mechanical chest compression devices respresents a new strategy that may result in improved survival.3, 4

Editor’s Capsule Summary

What is already known on this topic

Mechanical cardiopulmonary resuscitation (CPR) devices seem to improve outcome for out-of-hospital cardiac arrest in observational studies, but not in randomized controlled trials.

What question this study addressed

This meta-analysis pooled data from 5 randomized controlled trials and 15 observational studies on mechanical CPR in out-of-hospital cardiac arrest.

What this study adds to our knowledge

The pooled randomized controlled trials confirm that there is no apparent benefit to mechanical CPR over standard manual CPR in out-of-hospital cardiac arrest.

How this is relevant to clinical practice

This study supports manual CPR in out-of-hospital cardiac arrest, which is cheaper and technically easier to implement.

Given the often challenging conditions in the setting of an out-of-hospital cardiac arrest, a mechanical chest compression device could assist the rescuer to deliver high-quality CPR. Since the early 2000s, new devices have become clinically available that demonstrated improved blood pressure and coronary perfusion pressure compared with manual CPR.5, 6, 7 Thereafter, the first series of observational studies reported promising findings with regard to survival to admission.8, 9 Given the firm association between return of spontaneous circulation at hospital admission and survival to hospital discharge, a strategy that improves survival in the field is expected to result in higher survival to discharge. Unexpectedly, the first large randomized trial was halted because of evidence of unfavorable clinical outcome at discharge for the CPR strategy including a mechanical chest compression device.¹⁰ It has been suggested that study design and the choice of CPR algorithms affected the findings.¹¹ In the past year, the results of 3 large randomized controlled trials comparing mechanical with manual chest compressions in the out-of-hospital cardiac arrest setting have been published, thereby improving the available evidence on this topic.12, 13, 14

The present analysis addresses the collective evidence on this in-field intervention, presented for randomized and observational studies separately. In the context that differences in postresuscitation care may affect the initial advantage of a new out-of-hospital intervention and that a large part of the available data stems from observational studies, this meta-analysis primarily addresses survival to admission. Where this endpoint most directly reflects the acute effect of the intervention, the ultimate outcome measures concern survival to discharge and neurologic outcome. Evidence on these endpoints will be summarized as well for the studies with available data.