Mechanical chest compression machines for cardiac arrest

"Sudden cardiac arrest" occurs when someone's heart stops beating unexpectedly. Cardiopulmonary resuscitation, referred to as CPR, involves rhythmical pushing on the chest of a cardiac arrest victim to simulate the pump action of the heart. This can keep blood flowing to the victim's vital organs while the heart is not pumping. CPR has been shown to improve the chance that the heart will restart and the victim will survive. Machines have been developed to take over this chest pumping action using automated piston or band-like mechanisms. The theory is that these machines should be able to provide a more effective pumping action than is seen in humans because the machines do not pause or get tired, and they provide consistent pressure and timing of each chest compression. Some preliminary studies using these machines have shown that they are easy to use and can save people with cardiac arrest. We aimed to discover which method of chest compression (applying the traditional hand technique vs using a machine) results in more lives saved.

This is an update of the Cochrane review on mechanical chest compression devices published in 2011 (Brooks 2011). We updated our search strategy to January 2013. We searched the world literature and found 1871 citations that were potentially relevant. After reviewing each of these, we found that only six articles described clinical trials that could help us answer our question. Taken together, these trials included 1166 participants. The largest study found that patients who received treatment with a mechanical device had a lower chance of survival than patients treated with chest compressions applied by hand. Some problems were associated with the methods used in this trial, which may explain these unexpected results. Two smaller studies found that more patients treated with machine chest compressions had their hearts restart, but these studies were so small that the validity of this finding is unclear. Of the two new studies identified in this update, one demonstrated that patients in the group that received mechanical chest compressions more often had their heart restart and survived to the point of leaving the hospital when compared with patients who received chest compressions by hand. The other new study showed no difference between groups when researchers compared the likelihood of patients having their heart restart or being alive at the time of hospital admission or discharge.

The most important finding of our study was that not enough data are available from good-quality trials to answer our question and support a recommendation on whether these machines should be used. The current body of research comparing machine chest compressions versus hand chest compressions is not sufficient to indicate which technique is best. Very few studies have been conducted, and the studies reported had some major design problems. These studies provided results that are conflicting with respect to whether mechanical chest compressions improve survival. Several large randomised trials designed to answer this question are currently under way, and these results are expected in the next one to two years.

Authors' conclusions: 

Evidence from RCTs in humans is insufficient to conclude that mechanical chest compressions during cardiopulmonary resuscitation for cardiac arrest are associated with benefit or harm. Widespread use of mechanical devices for chest compressions during cardiac events is not supported by this review. More RCTs that measure and account for the CPR process in both arms are needed to clarify the potential benefit to be derived from this intervention.

Read the full abstract...

This is the first update of the Cochrane review on mechanical chest compression devices published in 2011 (Brooks 2011). Mechanical chest compression devices have been proposed to improve the effectiveness of cardiopulmonary resuscitation (CPR).


To assess the effectiveness of mechanical chest compressions versus standard manual chest compressions with respect to neurologically intact survival in patients who suffer cardiac arrest.

Search strategy: 

We searched the Cochrane Central Register of Controlled Studies (CENTRAL; 2013, Issue 12), MEDLINE Ovid (1946 to 2013 January Week 1), EMBASE (1980 to 2013 January Week 2), Science Citation abstracts (1960 to 18 November 2009), Science Citation Index-Expanded (SCI-EXPANDED) (1970 to 11 January 2013) on Thomson Reuters Web of Science, biotechnology and bioengineering abstracts (1982 to 18 November 2009), conference proceedings Citation Index–Science (CPCI-S) (1990 to 11 January 2013) and (2 August 2013). We applied no language restrictions. Experts in the field of mechanical chest compression devices and manufacturers were contacted.

Selection criteria: 

We included randomised controlled trials (RCTs), cluster RCTs and quasi-randomised studies comparing mechanical chest compressions versus manual chest compressions during CPR for patients with atraumatic cardiac arrest.

Data collection and analysis: 

Two review authors abstracted data independently; disagreement between review authors was resolved by consensus and by a third review author if consensus could not be reached. The methodologies of selected studies were evaluated by a single author for risk of bias. The primary outcome was survival to hospital discharge with good neurological outcome. We planned to use RevMan 5 (Version 5.2. The Nordic Cochrane Centre) and the DerSimonian & Laird method (random-effects model) to provide a pooled estimate for risk ratio (RR) with 95% confidence intervals (95% CIs), if data allowed.

Main results: 

Two new studies were included in this update. Six trials in total, including data from 1166 participants, were included in the review. The overall quality of included studies was poor, and significant clinical heterogeneity was observed. Only one study (N = 767) reported survival to hospital discharge with good neurological function (defined as a Cerebral Performance Category score of one or two), demonstrating reduced survival with mechanical chest compressions when compared with manual chest compressions (RR 0.41, 95% CI 0.21 to 0.79). Data from four studies demonstrated increased return of spontaneous circulation, and data from two studies demonstrated increased survival to hospital admission with mechanical chest compressions as compared with manual chest compressions, but none of the individual estimates reached statistical significance. Marked clinical heterogeneity between studies precluded any pooled estimates of effect.

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