CHICAGO, IL--The effectiveness of performing cardiopulmonary resuscitation (CPR) in cardiac arrest cases may have influenced the outcomes in one clinical trial, researchers suggested here.
Only about 40% of patients in the trial received CPR that was guideline compliant in delivering proper compression rate, compression depth and compression fraction, said Demetris Yannopoulos, MD, associate professor of medicine at the University of Minnesota, Minneapolis.
In his oral presentation at the American Heart Association Resuscitation Science Symposium, Yannopoulos said the failure to perform adequate CPR in the clinical part of a trial that tested an investigative active inspiratory impedance threshold device may have contributed to the neutral finding in the study.
The device worked well in animal models but did not show a difference in survival in patients, he said. And the confounding nature of performing CPR could have impacted the overall outcomes, he suggested.
Yannopoulos suggested that while performing chest compression at a rate of 80 to 120 compressions a minute was within guidelines, the failure to compress to a depth of more than 4-6 centimeters would make the number of compressions performed moot.
Similarly, if the compression fraction was less than 50% it would negate the compression rate and compression depth. All three factors had to be within guidelines (AHA 2005 recommendations or the study parameters) in order to have quality CPR, he said.
"If you don't have equality in performing CPR among groups, then you cannot assess improvements that could potentially lead to future improvements in outcome endpoints," he said.
The researchers analyzed data collected in the ROC (Resuscitation Outcomes Consortium)-PRIMED protocol through the National Institutes of Health data sharing policy, reviewing the electronically and prospectively recorded quality parameters which reflect the first 5 minutes of CPR, he said.
Data was available for 4,345 patients who were given a sham treatment and 4,374 patients who were treated with the actual device. He found that 72.9% of the sham patients received chest compressions within the guideline recommendations; 60.7% received compression depth as per guidelines and 88.5% of patients treated within the compression fraction goal of more than 50% as set by the trial protocol. But only 43.8% of patients received quality CPR – with doctors performing all 3 factors at the desired level.
In patients with the device, the results were similar: 75.3% of patients received adequate number of compressions; 61.2% received adequate depth compressions and 88.1% were within the desired compression fraction range – but just 45.6% of patients received all 3 factors within the target range.
The patients studied by Yannopoulos and his colleagues were about 67 years old and most (65%) were men. About 40% of the cardiac arrests were observed by a bystander; about 36% of the bystanders performed CPR. Emergency medical personnel arrived at the scene in less than 6 minutes after being dispatched, and advanced life support personnel were on the scene in about 8.5 minutes after the dispatch.
More than 99% of the patients in the study were treated by advanced life support teams. About 40% of the patients were given electric shocks. Successful intubation was performed in about 75% of the patients.
Yannopoulos said that if patients received acceptable compression rate, compression depth and compression fraction, 7.2% of the patients using the impedance threshold device survived to hospital discharge with a modified Rankin Score of less than 3 compared with 4.1% of patients assigned to use of the sham device (P=0.0064).
"The quality of CPR deliver to a cardiac arrest patient is an important national healthcare issue and may be an underappreciated effect modified in CPR clinical trials," Yannopoulos said. "Consideration of these observations is important for the appropriate design and execution of future resuscitation research, the interpretation of previous CPR studies and clinical resuscitation practice."
SOURCE: MedPage Today