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Continuous chest compressions during CPR failed to improve survival or neurologic function compared with standard chest compressions that are briefly interrupted for ventilation, based on findings in the first large randomized trial to compare the two strategies for out-of-hospital, nontraumatic cardiac arrest.
In a presentation at the American Heart Association scientific sessions, simultaneously published online Nov. 9 in the New England Journal of Medicine, Dr. Graham Nichol and his associates analyzed data from the Resuscitation Outcomes Consortium, a network of clinical centers and EMS agencies that have expertise in conducting research on out-of-hospital cardiac arrest.
Data were analyzed for 23,711 adults treated by 114 EMS agencies affiliated with eight clinical centers across the United States and Canada. These agencies were grouped into 47 clusters that were randomly assigned to perform CPR using either continuous chest compressions (100 per minute) with asynchronous positive-pressure ventilations (10 per minute) or standard chest compressions interrupted for ventilations (at a rate of 30 compressions per two ventilations) at every response to an out-of-hospital cardiac arrest. Twice per year, each cluster crossed over to the other resuscitation strategy, said Dr. Nichol of the University of Washington–Harborview Center for Prehospital Emergency Care and Clinical Trial Center in Seattle.
A total of 12,653 patients were assigned to continuous chest compressions (the intervention group) and 11,058 to interrupted chest compressions (the control group). The primary outcome – the rate of survival to hospital discharge – was 9.0% in the intervention group and 9.7% in the control group, a nonsignificant difference. Similarly, the rate of survival with favorable neurologic function did not differ significantly, at 7.0% and 7.7%, respectively, the investigators said (N Engl J Med. 2015 Nov 9. doi:10.1056/NEJMoa1509139).
The reason for these unexpected findings is not yet known. It is plausible that continuous chest compressions really don’t improve outcomes and that the previous positive results were actually due to improvements in the CPR process, such as more consistent rate and depth of compressions; concurrent improvements in the system of care; or Hawthorne effects, in which CPR providers altered their behavior during the studies because they were aware they were being observed.
However, it is also possible that three important limitations of this trial unduly influenced the results.
First, the per-protocol analysis, which used an automated algorithm to assess adherence to the compression assignments, could not classify many patients as having received either continuous or interrupted chest compressions. Second, the quality of postresuscitation care, which certainly influences outcomes, was not monitored. And third, actual oxygenation levels were not measured, nor were minutes of ventilation delivered. Thus, “we do not know whether there were important differences in oxygenation or ventilation between the two treatment strategies,” he said.
It is not yet clear why this large randomized trial showed no benefit from continuous chest compressions when previous observational research showed the opposite. One possibility is that many of the previous studies assessed not just chest compressions but an entire bundle of care related to CPR, so the benefits they reported may not be attributable to chest compressions alone.
In addition, in this study the mean chest-compression fraction – the proportion of each minute during which compressions are given, an important marker of interruptions in chest compressions – was already high in the control group (0.77) and not much different from that in the intervention group (0.83). Both of these are much higher than the target recommended by both American and European guidelines, which is only 0.60.
And of course a third reason may be that the interruptions for ventilation during CPR aren’t all that critical, and may be less detrimental to survival, than is currently believed.
Dr. Rudolph W. Koster is in the department of cardiology at Amsterdam Academic Medical Center. He reported having no relevant financial disclosures. Dr. Koster made these remarks in an editorial accompanying Dr. Nichol’s report (N Engl J Med. 2015 Nov 9. doi:10.1056/NEJMe1513415).
It is not yet clear why this large randomized trial showed no benefit from continuous chest compressions when previous observational research showed the opposite. One possibility is that many of the previous studies assessed not just chest compressions but an entire bundle of care related to CPR, so the benefits they reported may not be attributable to chest compressions alone.
In addition, in this study the mean chest-compression fraction – the proportion of each minute during which compressions are given, an important marker of interruptions in chest compressions – was already high in the control group (0.77) and not much different from that in the intervention group (0.83). Both of these are much higher than the target recommended by both American and European guidelines, which is only 0.60.
And of course a third reason may be that the interruptions for ventilation during CPR aren’t all that critical, and may be less detrimental to survival, than is currently believed.
Dr. Rudolph W. Koster is in the department of cardiology at Amsterdam Academic Medical Center. He reported having no relevant financial disclosures. Dr. Koster made these remarks in an editorial accompanying Dr. Nichol’s report (N Engl J Med. 2015 Nov 9. doi:10.1056/NEJMe1513415).
It is not yet clear why this large randomized trial showed no benefit from continuous chest compressions when previous observational research showed the opposite. One possibility is that many of the previous studies assessed not just chest compressions but an entire bundle of care related to CPR, so the benefits they reported may not be attributable to chest compressions alone.
In addition, in this study the mean chest-compression fraction – the proportion of each minute during which compressions are given, an important marker of interruptions in chest compressions – was already high in the control group (0.77) and not much different from that in the intervention group (0.83). Both of these are much higher than the target recommended by both American and European guidelines, which is only 0.60.
And of course a third reason may be that the interruptions for ventilation during CPR aren’t all that critical, and may be less detrimental to survival, than is currently believed.
Dr. Rudolph W. Koster is in the department of cardiology at Amsterdam Academic Medical Center. He reported having no relevant financial disclosures. Dr. Koster made these remarks in an editorial accompanying Dr. Nichol’s report (N Engl J Med. 2015 Nov 9. doi:10.1056/NEJMe1513415).
Continuous chest compressions during CPR failed to improve survival or neurologic function compared with standard chest compressions that are briefly interrupted for ventilation, based on findings in the first large randomized trial to compare the two strategies for out-of-hospital, nontraumatic cardiac arrest.
In a presentation at the American Heart Association scientific sessions, simultaneously published online Nov. 9 in the New England Journal of Medicine, Dr. Graham Nichol and his associates analyzed data from the Resuscitation Outcomes Consortium, a network of clinical centers and EMS agencies that have expertise in conducting research on out-of-hospital cardiac arrest.
Data were analyzed for 23,711 adults treated by 114 EMS agencies affiliated with eight clinical centers across the United States and Canada. These agencies were grouped into 47 clusters that were randomly assigned to perform CPR using either continuous chest compressions (100 per minute) with asynchronous positive-pressure ventilations (10 per minute) or standard chest compressions interrupted for ventilations (at a rate of 30 compressions per two ventilations) at every response to an out-of-hospital cardiac arrest. Twice per year, each cluster crossed over to the other resuscitation strategy, said Dr. Nichol of the University of Washington–Harborview Center for Prehospital Emergency Care and Clinical Trial Center in Seattle.
A total of 12,653 patients were assigned to continuous chest compressions (the intervention group) and 11,058 to interrupted chest compressions (the control group). The primary outcome – the rate of survival to hospital discharge – was 9.0% in the intervention group and 9.7% in the control group, a nonsignificant difference. Similarly, the rate of survival with favorable neurologic function did not differ significantly, at 7.0% and 7.7%, respectively, the investigators said (N Engl J Med. 2015 Nov 9. doi:10.1056/NEJMoa1509139).
The reason for these unexpected findings is not yet known. It is plausible that continuous chest compressions really don’t improve outcomes and that the previous positive results were actually due to improvements in the CPR process, such as more consistent rate and depth of compressions; concurrent improvements in the system of care; or Hawthorne effects, in which CPR providers altered their behavior during the studies because they were aware they were being observed.
However, it is also possible that three important limitations of this trial unduly influenced the results.
First, the per-protocol analysis, which used an automated algorithm to assess adherence to the compression assignments, could not classify many patients as having received either continuous or interrupted chest compressions. Second, the quality of postresuscitation care, which certainly influences outcomes, was not monitored. And third, actual oxygenation levels were not measured, nor were minutes of ventilation delivered. Thus, “we do not know whether there were important differences in oxygenation or ventilation between the two treatment strategies,” he said.
Continuous chest compressions during CPR failed to improve survival or neurologic function compared with standard chest compressions that are briefly interrupted for ventilation, based on findings in the first large randomized trial to compare the two strategies for out-of-hospital, nontraumatic cardiac arrest.
In a presentation at the American Heart Association scientific sessions, simultaneously published online Nov. 9 in the New England Journal of Medicine, Dr. Graham Nichol and his associates analyzed data from the Resuscitation Outcomes Consortium, a network of clinical centers and EMS agencies that have expertise in conducting research on out-of-hospital cardiac arrest.
Data were analyzed for 23,711 adults treated by 114 EMS agencies affiliated with eight clinical centers across the United States and Canada. These agencies were grouped into 47 clusters that were randomly assigned to perform CPR using either continuous chest compressions (100 per minute) with asynchronous positive-pressure ventilations (10 per minute) or standard chest compressions interrupted for ventilations (at a rate of 30 compressions per two ventilations) at every response to an out-of-hospital cardiac arrest. Twice per year, each cluster crossed over to the other resuscitation strategy, said Dr. Nichol of the University of Washington–Harborview Center for Prehospital Emergency Care and Clinical Trial Center in Seattle.
A total of 12,653 patients were assigned to continuous chest compressions (the intervention group) and 11,058 to interrupted chest compressions (the control group). The primary outcome – the rate of survival to hospital discharge – was 9.0% in the intervention group and 9.7% in the control group, a nonsignificant difference. Similarly, the rate of survival with favorable neurologic function did not differ significantly, at 7.0% and 7.7%, respectively, the investigators said (N Engl J Med. 2015 Nov 9. doi:10.1056/NEJMoa1509139).
The reason for these unexpected findings is not yet known. It is plausible that continuous chest compressions really don’t improve outcomes and that the previous positive results were actually due to improvements in the CPR process, such as more consistent rate and depth of compressions; concurrent improvements in the system of care; or Hawthorne effects, in which CPR providers altered their behavior during the studies because they were aware they were being observed.
However, it is also possible that three important limitations of this trial unduly influenced the results.
First, the per-protocol analysis, which used an automated algorithm to assess adherence to the compression assignments, could not classify many patients as having received either continuous or interrupted chest compressions. Second, the quality of postresuscitation care, which certainly influences outcomes, was not monitored. And third, actual oxygenation levels were not measured, nor were minutes of ventilation delivered. Thus, “we do not know whether there were important differences in oxygenation or ventilation between the two treatment strategies,” he said.
FROM THE AHA SCIENTIFIC SESSIONS
Key clinical point: Continuous chest compressions during CPR didn’t improve survival or neurologic function compared with standard compressions briefly interrupted for ventilation.
Major finding: The primary outcome – the rate of survival to hospital discharge – was 9.0% for continuous chest compressions and 9.7% for interrupted compressions, a nonsignificant difference.
Data source: A cluster-randomized crossover trial involving 23,711 adults treated by 114 North American EMS agencies for nontraumatic out-of-hospital cardiac arrest.
Disclosures: This study was supported by the U.S. National Heart, Lung, and Blood Institute, the U.S. Army Medical Research and Materiel Command, the Canadian Institutes of Health Research, the Institute of Circulatory and Respiratory Health, Defence Research and Development Canada, the Heart and Stroke Foundation of Canada, the American Heart Association, and the Medic One Foundation. Dr. Nichol and his associates reported ties to numerous industry sources.