Survival Rates Jump in New Cardiac Arrest Study

     There's a lot that goes into good CPR. But when it all comes together optimally, a new study demonstrates, it produces significant benefit.

     Data collected in seven cities showed that rates of survival to hospital discharge doubled when victims of out-of-hospital cardiac arrest received consistently good CPR (delivered per the American Heart Association's 2005 guidelines), including use of an impedance threshold device (i.e., Advanced Circulatory Systems' ResQPOD). The results were presented at the AHA's Scientific Sessions, held late last year in Orlando.

     When nearly 900 patients got this level of care, 15.7% survived to hospital discharge—roughly twice the rate of the control group (7.9%). That's one of the highest overall survival rates ever documented for out-of-hospital cardiac arrests, says lead author Tom Aufderheide, MD, director of the Medical College of Wisconsin's Resuscitation Research Center.

     "And it wasn't just paramedic-witnessed VF patients," Aufderheide notes. "This was asystole, flatlined, pulseless electrical activity, unwitnessed, witnessed—everybody. The average survival rate nationally, taken that way, is around 5%. So we were thrilled with the data, and I'm encouraged that we can improve on it even further."

     The study examined quality assurance data from seven systems that use the ResQPOD: the Madison (Wisc.) Fire Department, Allina Medical Transportation (Anoka Co., Minn.), Wake County EMS (Raleigh, NC), Pinellas County EMS (Largo, Fla.), Omaha (Neb.) Fire Department, Cypress Creek (Tex.) EMS and the Medical College of Wisconsin. These systems all implemented the "new" CPR, including more compressions per minute, continuous compressions during ALS, full chest-wall recoil and use of the ITD, which increases blood flow to vital organs by way of inspiratory impedance. A Class IIa recommendation from the AHA (the second-highest rating possible, and the highest given to any drug or device used for increasing circulation during CPR or improving resuscitation rates), an impedance threshold device works by stopping incoming respiratory gases during each recoil, thus reducing intrathoracic pressure and drawing more blood back to the heart. This in turn produces more outflow from the heart during the next compression. The ResQPOD is the only ITD on the U.S. market.

     The data was compared to historical or concurrent control data. In addition to the increase in survival to hospital discharge, patients getting the new CPR with ITD also showed greater rates of return of spontaneous circulation (37.9% vs. 33.8%).

     "What it means is that we're bringing slightly more patients in to the hospital, but of those patients who arrive there, twice as many survive to being discharged," Aufderheide says. "And we believe that's the result of significantly improved hemodynamics from CPR."

     Four of the seven participating systems also captured neurological outcome data. Outcomes appeared slightly better in the new CPR group, Auferheide says, though the improvement did not reach statistical significance.

     Are these survival rates as high as they can go? Obviously, more study is warranted. The recent trend toward reduced ventilations, reflected in the AHA guidelines and promoted by various cardiac experts, seems to be producing positive results, but the most effective possible blend of compressions, ventilations and accessories like the ITD has not yet been concretely identified.

     "We've all recognized now that a reduced-ventilation strategy results in improved hemodynamics during CPR and improved outcome; the only controversy is the degree to which ventilations are reduced," Aufderheide says. "I think they can probably be reduced even more and remain effective. But I believe intermittent ventilations are crucially important, and determining the optimal balance is an important area for further research."

     For more: www.americanheart.org, www.advancedcirculatory.com.