Mixed Message for Automated vs. Manual CPR

SEATTLE, June 19 ? In a pair of chest-to-chest trials, an automated compression device came up the winner in one but traditional manual CPR did better in the other.

In the first study, a multicenter, cluster-randomized trial of patients in the U.S. and Canada having an out-of-hospital cardiac arrest, the four-hour survival time from the 911 call was similar for both automated and manual CPR patients, according to a report in the June 14 issue of the Journal of the American Medical Association.

However, the independent data and safety monitoring board recommended early termination of enrollment because of lack of benefit in survival for four hours and possible harm in secondary, longer patient-centered outcomes, Al Hallstrom, Ph.D., of the University of Washington here and colleagues reported.

The FDA-approved automated device used in this study is a load-distributing band, a labor-saving circumferential chest compression device with an electrically activated constricting band that produces greater blood flow to vital organs.

To compare resuscitation outcomes, 554 patients received standard EMS care with a load-distributing band device, while 517 were given manual CPR. A primary comparison population included 726 individuals in cardiac arrest at the time of EMS arrival who were chosen before-hand as the population most likely to benefit from chest compression.

Four-hour survival time after the 911 call was similar for both techniques (29.5% vs 28.5%; P=.74). There were also no differences in the primary study population (24.7% vs. 26.4%, respectively, P= .62), the researchers reported.

However, in the primary population, survival to hospital discharge was 5.8% in the load-distributing band group compared with 9.9% in the manual CPR group (P=.06, adjusted for covariates and clustering), the researchers reported.

A cerebral performance rating of 1 or 2 at hospital discharge was recorded for 3.1% in the load-distributing band patients versus 7.5% in the manual CPR group (P=.006), the researchers said.

Increased blood flow during CPR should translate to a higher likelihood of successful resuscitation, the researchers said, adding that the results of this trial "were not expected and there is no obvious explanation."

However, one possible explanation, Dr. Hallstrom suggested, is that the manual CPR quality initially exceeded standard practice, or that there could have been a learning curve for use of the device with performance expected to improve over time.

The results of this study underscore the complexity of resuscitation from out-of-hospital cardiac arrest, the researchers said. Further research, they added, is required to understand the interaction of chest compression with other aspects of resuscitation, such as the phase of the arrest, drug choice and dose, and timing of defibrillation.

Finally, Dr. Hallstrom said, device design and implementation strategies may need further preclinical evaluation.

The researchers noted that the study was sponsored by Revivant Corporation, now part of the Zoll Corporation, maker of the AutoPulse Resuscitation system used in this study. Dr. Vince Mosesso, Jr., M.D., a study co-author reported receiving equipment and supplies for a clinical trial from the Zoll corporation.

In the second JAMA study, researchers reported apparently contradictory results. Rates for survival to hospital admission and survival to discharge were higher among the load-distributing band patients, while no significant differences were found between the groups for neurologic outcomes, according to Joseph Ornato, M.D., at Virginia Commonwealth University in Richmond and colleagues.

The study, a phased observational cohort evaluation of 783 adults with out-of-hospital, nontraumatic cardiac arrest, compared outcomes before (499 patients) and after (284 patients) an EMS service switched from manual CPR to automated load-distributing band CPR.

Patients in the manual and automated CPR groups were comparable except for a faster response time (mean difference, 26 seconds) and more EMS-witnessed arrests (18.7% vs 12.6%) for patients given load-distributing band CPR, the researchers reported.

Rates for the return of spontaneous circulation and survival were increased with load-distributing band CPR compared with manual CPR. Other results for load-distributing band CPR versus CPR were as follows:

For return of spontaneous circulation, 34.5% (95% CI 29.2%-40.3%) vs 20.2% (CI, 16.9%-24.0%); adjusted odds ratio (OR), 1.94 (CI, 1.38-2.72);

For survival to hospital admission, 20.9% (CI, 16.6%-26.1%) vs 11.1% (CI, 8.6%-14.2%); adjusted OR, 1.88 (CI, 1.23-2.86);

Rates for survival to hospital discharge were also significantly better for the LDB patients: 9.7% (CI, 6.7%-13.8%) vs 2.9% (CI 1.7%-4.8%); adjusted OR, 2.27 (CI, 1.11-4.77).

In a secondary analysis of the 210 patients treated with the load-distributing band device, 38 patients (18.1%) survived to hospital admission (CI, 13.4%-23.9%) and 12 patients (5.7%) survived to hospital discharge (CI, 3.0%-9.3%), the researchers reported.

Finally, among all the patients who survived to hospital discharge, there were no significant differences in Cerebral Performance Category (P=.36) or Overall Performance Category (P=.40).

The main limitation of the study, the researchers noted was that it was not a randomized, controlled trial. Despite this, they said they believe the results are valid because the patients were comparable even after adjusting for a slightly faster EMS response time and for more frequent EMS-witnessed events.

The study suggests that resuscitation with automated load-distributing band CPR on rapidly responding EMS ambulances is associated with improved outcomes, including survival to hospital discharge, Dr. Ornato said.

"These results," he wrote, "suggest that the load-distributing band device may be a useful addition to current cardiac treatment options, especially when used early for patients who do not respond immediately to a brief period of manual CPR, defibrillation, or both."

However, the researchers added that a large, adequately powered, prospective randomized and blinded clinical trial is needed to further define the value of LDB in resuscitation.

Dr Ornato disclosed that he is a science adviser for ZOLL Circulation of Sunnyvale, Calif., the manufacturer of the Autopulse device used in the study. Also, ZOLL Circulation provided LDB devices used during various phases of the study.

Attempting to determine whether the differing conclusions of these two studies can be reconciled, editorial writers Roger J. Lewis, M.D., Ph.D, and James Niemann, M.D., of the University of California Los Angeles, said the apparent contradictions lead to several critical questions, including whether the true effectiveness of the device was different in the two settings.

Other issues, they wrote, were possible differences in the patient populations and how the device was incorporated into treatment; whether there was a methodological weakness in the design, conduct, or analysis of one or both studies; and whether anomalous outcome patterns occurred by chance.

Summing up, they said that although it is not possible to reach definitive conclusions until additional data are available, the best current information suggests that the degree of benefit or harm associated with the use of the device, is influenced by how it is used, including selection of the patient population with respect to presenting rhythm, time from arrest to start of CPR, and time to deployment and the influence of deployment on time to defibrillation, when appropriate.

"To shed light on these questions," they wrote, "future comparative studies will need to pay particular attention to the definitions and consistency of the method of use of the device, to measuring the multiple important time intervals with precision, and to ensuring the quality of the manual CPR administration in both trial groups."