AutoPulse Cardiac Pump Shows Promise in Pair of EMS Studies

It was never supposed to be an outcome study. But then buzz on the street began.

“Paramedics started coming to us and saying this machine was providing miraculous, lifesaving results,” says Marshal Isaacs, MD, EMS Medical Director for the San Francisco Fire Department (SFFD). “After we started hearing story after story, we applied for [IRB] approval to actually collect data and try to look scientifically at the results.”

That led to one of a pair of new studies that suggest that the ZOLL AutoPulse Non-Invasive Cardiac Support Pump—which automates chest compressions during CPR (see photo at right)—may help increase short-term survival in patients who have cardiac arrests.

The San Francisco study compared the effects on similar patients of using the AutoPulse vs. standard CPR.1 The SFFD had originally placed four AutoPulses in the field to get a sense of their reliability and ease of use. What they found instead, once they started collecting and crunching data, was that the delivery to emergency departments of patients with beating hearts rose by 35%.

“Even with limitations in methodology and operations,” says Isaacs, “the data showed that more patients without shockable rhythms arrived at the ED with pulses in the AutoPulse group than in the standard CPR group. Those numbers were statistically significant.”

The department deployed the AutoPulses with paramedic supervisors who used them when they encountered arrests in progress. Using age, gender and length of resuscitation efforts, results from the AutoPulse cases were then compared to results from comparable cases in which standard CPR was used, with a primary endpoint of patient arrival at the ED with spontaneous circulation.

The AutoPulse showed an improvement: 39% of patients on whom it was used had ROSC upon ED arrival, while 29% of regular-CPR patients did. This improvement was clearest among those with initial presenting rhythms of asystole (37% vs. 22%) or pulseless electrical activity (38% vs. 23%).

Some cautions, though: Because the SFFD’s investigation was not designed as an outcome study, its methodology was not optimal—case-matching is a fairly imprecise way to compare results. Also, because it had only four devices, the department gave them to the roving supervisors, who responded to every arrest, but not with the first-arriving crews. “And that,” says Isaacs, “is where you’d expect that a device that provides tremendous CPR and doesn’t fatigue, like a rescuer would, to have its greatest benefit—in the first few minutes of an arrest.”

At roughly the same time, a study in Richmond, VA, was showing similar promise.2 This study compared ROSC percentages in adult non-traumatic cardiac arrests from five years before and six months following a switch to the AutoPulse. Investigators found that using the AutoPulse yielded a 74% relative increase in ROSC over standard CPR. This increase occurred regardless of the patient’s initial cardiac rhythm. Overall, ROSC for all patients increased from 21.6% to 37.5%.

Further research is, of course, needed, and is ongoing. But the early indications suggest that optimizing CPR compressions automatically may be a big benefit to patients.

“Our paramedics said patients would practically sit up and talk,” says Isaacs. “When it wasn’t running, they were unconscious and pulseless. But with it providing CPR, they’d get strong pulses, the patients’ color would improve, their oxygenation, their end-tidal CO2—all the parameters saying that good blood flow, perfusion and circulation were taking place. We are very encouraged by the results.”

References

1. Casner MJ, Andersen DW, Isaacs M. A retrospective, case-matched review of the effect of a CPR assist device on survival from out-of-hospital cardiac arrest. Preh Emer Care 9(1), Jan.–Mar. 2005.

2. Ornato JP, et al. Improvement in field return of spontaneous circulation using circumferential chest compression cardiopulmonary resuscitation. Presented at NAEMSP annual meeting, Jan. 13–15, 2005, Naples, FL.