Roseville, MN - A pair of devices for assisting paramedics performing cardiopulmonary resuscitation (CPR) for out-of-hospital cardiac arrest can raise the patient's chances of discharge with good neurologic function, suggests a randomized trial published this week .
One of the devices (ResQPump, Advanced Cardiovascular Systems, Santa Clara, CA) is essentially a double-grip handle that attaches to the patient's chest with a suction cup, allowing the rescuer to push for delivering compressions and lift for decompressions. An impedance-threshold valve (ResQPOD, Advanced Cardiovascular Systems) in the patient's mouth limits passive lung inflation during the chest-decompression phase, boosting intrathoracic pressures and enhancing perfusion of the heart and brain, as Dr. Tom P Aufderheide (Medical College of Wisconsin, Milwaukee) and colleagues describe in the January 22, 2011 issue of the Lancet. Their report was published online January 18.
Patients getting the active compression-decompression CPR (n=840) also showed significantly greater survival at one year than those who had standard manual CPR (n=813). Neurologic function held steady in both groups from 90 days to one year.
Based on the trial and earlier small clinical and animal studies, “active compression-decompression CPR with augmentation of negative intrathoracic pressure should be considered as an alternative to standard CPR to increase long-term survival after cardiac arrest,” the group writes.
The ResQPOD impedance-threshold valve is available in the US; the trial is expected to help the company make the ResQPump's approval case before the FDA.
There’s solid evidence that the combined technique can lower intracerebral pressure and improve brain perfusion; animal studies show it raises carotid blood flow, according to Dr. Michael Sayre (Ohio State University, Columbus), who isn’t involved with the current study but told heartwire that it’s convincing.
Moreover, the study suggests that the device-assisted CPR technique can be generalized across different emergency medical services (EMS), which spanned five states.
“I think they showed that this combination of devices in a variety of different EMS system really did seem to make a positive impact on survival,” said Sayre, who chairs the American Heart Association Emergency Cardiovascular Care Committee.
“Should the findings of the [current] trial change clinical practice and lead to a widespread use of active compression-decompression and impedance-threshold devices for out-of-hospital cardiac arrest? Probably not yet,” according to Dr. Peter Nagele (Washington University School of Medicine, St Louis, MO) in an accompanying editorial .
Previous clinical studies of CPR with the ResQPump and ResQPOD, either alone or in combination, have produced mixed results, Nagele writes. Enrollment in the current trial was less than planned, and “a larger cohort could have changed the findings.” And although the analyses were conducted with blinding to treatment group, rescuers could not be blinded to which CPR method they used. So “replication of the combined technique is needed.”
Certainly, there is the possibility of bias because of difficulties in blinding treatment, Sayre noted. “On the other hand, it's still a positive result. If paramedics are more enthusiastic and able to perform better CPR because of the devices, for whatever reason, and patients survive, that's a good thing.”
The trial included 46 EMS agencies in urban, suburban, and rural regions in Washington and four Midwest states; 4,940 EMS personnel were trained in the active compression-decompression CPR technique before the study and then every six months.
Eligible patients experiencing presumed cardiac arrest were randomized over about three and a half years to undergo CPR either with or without the active compression-decompression technique.
The hospital-survival rate was statistically similar in the intervention and control groups, but the primary end point of hospital discharge with good neurologic function (defined as a modified Rankin score <3) was significantly higher in the intervention group (odds ratio 1.58, 95% CI 1.07-2.36; p=0.019). Those patients also showed better one-year survival, but a significantly increased rate of pulmonary edema.
Discharge with favorable neurologic function, survival, and adverse event rates, CPR with ResQ interventions vs standard CPR
The clinical relevance of more pulmonary edema in the intervention group is “unclear,” the group writes, as the magnitudes of the increased risk and survival benefit are similar.
Sayre pointed out that the >50% magnitude of benefit “is very comparable to other sorts of interventions in cardiology.” The survival gains in absolute numbers may be small, but out-of-hospital cardiac arrest is common enough for them to translate into a substantial number of lives saved.
“We've been doing the same form of CPR for the past 50 years, and we really haven’t made big progress in terms of improving outcomes for these patients,” he observed. “And really in the past five to 10 years we’ve seen glimmers of opportunity, with things like therapeutic hypothermia for comatose survivors of out-of-hospital arrest and improved attention to detail about CPR itself, and now with devices like this [ResQPump/ResQPOD] combination.”
With each improvement, Sayre said, “I think we're getting 2% or 3% more survivors, and after a while that starts to add up.”
 Aufderheide TP, Frascone RJ, Wayne MA, et al. Standard cardiopulmonary resuscitation versus active compression-decompression cardiopulmonary resuscitation with augmentation of negative intrathoracic pressure for out-of-hospital cardiac arrest: a randomised trial. Lancet 2011; 377:301-311.