"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.