Two studies comparing manual and machine-generated chest compressions during cardiopulmonary resuscitation (CPR) have produced conflicting results. One study involved about 1,100 patients who had an out-of-hospital cardiac arrest. Researchers compared survival rates of those who received manual chest compression with those who received compressions delivered via a load-distributing band (LDB), which wraps around a patient's chest and attaches to a backboard.

Survival rates were similar for both types of CPR: 29.5% for manual CPR and 28.5% with the automatic device. Researchers noted, however, that the automatic device was linked to worse neurologic outcomes than manual CPR.

A second study involved 783 patients who experienced out-of-hospital cardiac arrest. These patients received care from an emergency medical system that had switched from manual CPR to the LDB system of chest compressions. Researchers found significant improvement in survival rates within the first 4 hours after cardiac arrest among patients treated with the LDB. Survival rates among LDB-treated patients also improved until the time of hospital discharge: 9.7% survival rates in patients who received LDB treatment compared with 2.9% for those who had manual compressions.

Apparently the jury is still out on whether automated chest compressions improve outcomes.

Sources