"Sudden cardiac arrest" occurs when someone's heart stops beating unexpectedly. Cardiopulmonary resuscitation referred to as CPR involves the rhythmically 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 chances that the heart restarts and the victim survives. 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 humans because the machine will not pause or get tired and will provide a 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 compressions (the traditional hand technique versus using a machine) results in more lives saved.
We searched the world literature and found 1561 articles which were potentially relevant. After reviewing each of these, we found that only 4 articles described clinical trials that could help us answer our question. All together, these trials included 868 patients. The largest and most recent study found that patients who received treatment with a mechanical device had lower chances of survival compared with patients treated with chest compressions by hand. There were some problems 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 have their hearts restart but the studies were so small that the validity of this finding is unclear.
The most important finding of our study was that there is not enough data from good quality trials to answer our question and provide a recommendation on whether or not these machines should be used. The current body of research comparing machine chest compressions with hand chest compressions is not sufficient to decide which is the best technique to use. There have been very few studies and they have some major design problems. They provide results which are conflicting with respect to whether mechanical chest compressions improve survival or not. Good quality randomised controlled studies are urgently needed.