AutoPulse

Overview
The AutoPulse is an automated cardiopulmonary resuscitation machine created by Revivant and subsequently purchased by ZOLL. It is a circumferential chest compression device composed of a constricting band and half backboard that is intended to be used as an adjunct to CPR during advanced cardiac life support by paramedics. The 2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation give load-distributing band CPR (LDB-CPR) a Class IIb recommendation.

Device operation
The patient's head, shoulders and upper back lay upon the base unit, with the controls for the AutoPulse beside the patient's left ear. It can be augmented for cervical spinal support. The unit contains the control computer, the rechargeable battery, and the motors that operate the LifeBand. The LifeBand is an adjustable strap that covers the entire rib cage. When the patient (who must be disrobed) is strapped in and the start button is pressed, the LifeBand pulls tight around the chest and proceeds to rhythmically constrict the entire rib cage, compressing and pumping the heart at a rate of 80 beats per minute equivalent. The LifeBand can be placed over AED pads but must be taken off to use standard paddle defibrillators. The LifeBand is disposable, and designed to be used on a single patient for sanitary reasons.

Studies and clinical trials
The gold standard for resuscitation research is survival to hospital discharge. Although common sense suggests that short-term and intermediate outcomes like return of spontaneous circulation (ROSC) or survival to hospital admission are promising, experienced scientists know that anything less than a neurologically intact survivor walking out of the hospital is ultimately irrelevant.

Several animal studies have shown that automated CPR machines are more effective at providing circulatory support than manual CPR. One study showed that use of the AutoPulse produced blood flow to the heart and brain that was comparable to pre-arrest levels. In another study, an adapted AutoPulse was shown to be highly effective in support of cardiac arrest in animals, whereas manual CPR was tenuous in its effectiveness. Pigs were used in the study, and were left in cardiac arrest for eight minutes to simulate average ambulance response time. 73% of the pigs that were put into the AutoPulse were revived, and 88% of the surviving pigs showed no neurological damage. None of the pigs that received manual CPR survived.

The device has shown less promise with human research. Although some studies showed improved coronary perfusion pressure and more spontaneous return of circulation with the AutoPulse, one large, multi-centered, randomized clinical trial was canceled early by the Institutional Review Board (IRB) when it was determined that patients who received manual CPR were more likely to walk out of the hospital, suggesting that enthusiasm for the device "is premature, given that the effectiveness of the device likely depends on still-to-be-defined factors independent of the mechanical capabilities of the device."

AutoPulse in the news
ABC World News Tonight on May 19, 2005, did a story on automated CPR machines, and profiled the story of Caralee Welch, who survived thirty minutes of cardiac arrest during which the AutoPulse was used. She had a heart attack in front of a theatre, but even after a half-hour of no heartbeat, with AutoPulse's help she ultimately recovered with no apparent brain damage.