Conflicting data regarding the AutoPulse battery-operated mechanical chest compression device could be clarified with the Circulation Improving Resuscitation Care (CIRC) trial, a randomized controlled trial that addresses methodological issues that may have influenced the results of previous studies, according to description of the trial in the March issue of Resuscitation.
Animal and human studies have shown that AutoPulse (Zoll Medical) cardiopulmonary resuscitation (CPR) improves hemodynamic parameters over manual CPR. However, human studies conducted in the prehospital setting have conflicting results as to the AutoPulse's efficacy in improving survival.
In particular, a randomized controlled trial was terminated early when no difference was found in survival to four hours, and survival and cerebral performance at hospital discharge were worse with AutoPulse CPR (JAMA 2006;295:2620–2628). "However, potential problems with the methodology of this trial have been identified," according to researchers.
One of the methodological problems with the previous randomized controlled study was that the AutoPulse arm had a delay to first chest compressions compared with the manual chest compression arm. To correct for that bias, the CIRC trial will integrate AutoPulse CPR after manual CPR.
Led by E. Brooke Lerner, PhD, from the Medical College of Wisconsin in Milwaukee, researchers will determine if integrated AutoPulse CPR is superior, inferior or equivalent in survival to hospital discharge compared with manual CPR. The secondary objectives are comparisons of sustained return of spontaneous circulation (ROSC), survival to 24 hours and neurologic status at hospital discharge.
The required sample size is expected to lie between 2,500 and 4,000, but may be higher or lower since the trial is stopped as soon as a conclusion can be reached, researchers noted.
The trial has six "unique" features:
- Training of all EMS providers in a standardized deployment strategy that reduces hands-off time and continuous monitoring for protocol compliance.
- A pre-trial simulation study of provider compliance with the trial protocol.
- Three distinct study phases (in-field training, run-in and statistical inclusion) to minimize the Hawthorne effect and other biases.
- Monitoring of the CPR process using either transthoracic impedance or accelerometer data.
- Randomization at the subject level after the decision to resuscitate is made to reduce selection bias.
- Use of the Group Sequential Double Triangular Test with sufficient power to determine superiority, inferiority or equivalence.
A standardized four-hour training program was developed focusing on reducing hands-off time.
Providers are trained in and practice the "pit crew" model of resuscitation. "This minimizes interruptions of manual CPR by assigning providers to specific duties based on their position next to a patient. Integrating manual CPR with AutoPulse CPR, using assigned roles, and a standardized deployment method are intended to reduce hands-off time, especially during device deployment, which was identified as a problem in a previous study," investigators wrote.
They concluded, "This unique, large, multicenter study comparing the effectiveness of integrated AutoPulse CPR to manual CPR will contribute to the science of the treatment of out-of-hospital cardiac arrest as well as to the design of future trials."