You Take My Breaths Away
Promotional material for this month's Emergency Cardiovascular Care Update conference calls it "the most controversial topic emerging following the 2005 AHA guidelines." Continuous chest compression CPR has generated a lot of discussion among the nation's cardiacademia, with its proponents touting increases in neurologically intact survival rates, and others urging caution in any movement away from ventilations.
On page 41, authors led by Gordon Ewy, MD, director of the University of Arizona's Sarver Heart Center, discuss the benefits of the CCC CPR model implemented in their jurisdictions, and in this article, a number of top experts offer perspectives on it and the AHA's recent "hands-only" advisory statement for bystanders.
This spring, the American Heart Association gave its blessing to bystanders of witnessed collapses using "hands-only" CPR, eliminating the rescue breaths many Americans feel uncomfortable doing. Going even further, some jurisdictions, as described in the accompanying article, now have their responders delivering continuous chest compression CPR, also known as cardiocerebral resuscitation, or CCR.
The AHA believes hands-only CPR is as good as conventional CPR (i.e., the 30:2 model) when a cardiac arrest victim goes down. Proponents of CCR believe it can produce more survivors, and more of them neurologically intact. Time and more research will tell, but for now, what should EMS providers know about each?
HANDS-ONLY CPR
What you should know about the AHA's new position is that it doesn't apply to you. It's for civilians who witness out-of-hospital cardiac arrests of adults. It pertains to EMS only in its training of the public.
Upon witnessing a collapse, bystanders are advised to call 9-1-1, then begin pushing hard and fast in the middle of the chest, 100 times a minute with minimal interruptions. If an AED is available, it should be used. Exceptions are infants and children, adults who are found unconscious and not breathing normally, and victims of drowning and other kinds of respiratory arrest. For them (and for rescuers who are proficient with it), conventional CPR can still used.
The idea is not that hands-only is better, but that it does as well as conventional CPR, and will be easier to coach and perform.
"For bystanders who perform CPR on victims of witnessed ventricular fibrillation cardiac arrest, the outcomes seem to be roughly the same regardless of whether they give ventilations," says Michael Sayre, MD, who chaired the committee that wrote the AHA's new policy. "The problem is that the majority of cardiac arrest events today aren't getting any form of bystander CPR, and part of the reason is that the instructions we've been providing are just too complicated. Our hope is that by encouraging people to give chest compressions, we can see more bystander CPR being done."
Upon collapse, a victim's arterial oxygen content is usually sufficient to oxygenate the heart and brain; the key is getting the blood moving, via compressions, then keeping it moving by minimizing interruptions. Ventilations certainly still have some role to play; the key is figuring out what's ideal. Many experts believe they can be safely reduced from current levels.
"In the first few minutes after a sudden collapse, you're likely fine without the breaths," says Paul Pepe, MD, MPH, medical director for Dallas area and a veteran researcher in the resuscitation fields. "You can do compressions only, and on balance you're going to have better outcomes. After four or five minutes, at least, you probably need to give an occasional breath, but I think we need to do it at lower rates than we've used in the past."
"By four minutes and beyond, oxygen becomes a very important aspect of resuscitation," says Mickey Eisenberg, MD, PhD, medical director for King County (WA) EMS and a top authority in prehospital cardiac arrest. "What's important is to figure out the best balance"—that is, the optimal number, frequency and timing of ventilations to most effectively help SCA victims.
The other aspect to the AHA change is getting people to do something. Bystander CPR rates remain low, and improving them is critical to increasing save rates.
"We believe people are more likely to do CPR if they don't have to worry about the ventilation component," says Vinay Nadkarni, MD, cochair of the International Liaison Committee on Resuscitation (ILCOR) and a spokesman for the AHA. "The data shows that hard, fast, near-continuous chest compressions, particularly by bystanders, save lives. And it appears from the literature that with coaching, people can deliver near-continuous chest compressions effectively. So with that combination of data, we've reached a tipping point that allows the AHA to increase its emphasis on chest compressions early in the resuscitation."
The AHA previously approved hands-only CPR for certain 9-1-1 callers being coached by emergency call-takers, and it's used in numerous U.S. jurisdictions. Results have been mixed; most recently, a review in the April issue of Resuscitation found that only 15% of eligible victims in such a system actually received chest compressions before EMS' arrival.
Now, with the new distinction between witnessed and unwitnessed collapses, and exceptions for respiratory arrests, prearrival instructions could take on even greater importance.
"The dispatcher will have to sort out whether it's a witnessed or an unwitnessed event, and that should allow a more focused message to the bystander," says Eisenberg. "Personally I think we need major efforts to promote dispatcher-assisted bystander CPR. There is great potential for dispatch centers to increase CPR rates in their communities."
"There's huge room for improving the instructions we give," adds Sayre. "What, specifically, do we tell people? I think we can learn more about using the right words to motivate people to act, and further simplifying the instructions, so we can get people to do what needs to be done."
CARDIOCEREBRAL RESUSCITATION
There was little controversy surrounding the AHA's new position. That's less true with CCR.
"I think we're all in synch in terms of minimally interrupting compressions," says Pepe, "but I'm not totally supportive of the concept that once a first responder gets there, we don't give any breaths. From a physiological point of view, after four or five minutes, I think you probably need occasional lung inflation in most people."
"Further studies are needed before we come to any conclusions about professional rescuers not breathing for patients," says Tom Aufderheide, MD, director of the Resuscitation Research Center at the Medical College of Wisconsin.
Aufderheide points to recent research in animal models that raises concerns that not breathing can precipitate a rapid collapse of the lungs.
"Research I've been involved with indicates that when you never breathe for an animal in cardiac arrest, you get lung atelectasis rather quickly," he says. "As that continues, you get distortion of the pulmonary architecture. Blood is impeded flowing through the lungs, and forward blood flow is compromised. I think this is critical: How do you restore the normal architecture of the lungs? With intermittent positive-pressure breathing!"
While recent literature on CCR is intriguing, it's not yet overwhelming. In the Arizona study published in the March 12 Journal of the American Medical Association, which tracked survival to hospital discharge, BVM ventilation was allowed, and the starting overall survival rate was just 1.8% (it improved to 5.4%, 17.6% for witnessed v-fib arrests). The 2006 report from Wisconsin, which looked at neurological outcomes, had small numbers; a pending update increases them, but shows moderate declines in overall survival (47%, vs. 58% in 2006) and neurological normalcy (39%, vs. 48% in 2006).
Still, the pre-CCR Wisconsin numbers were a respective 20% and 15%, so major improvement remains.
"I think the concept of cardiocerebral resuscitation has a lot of value, because of course it's brain function and quality of life that we really want to restore," says Nadkarni. "The good thing is that these systems that have adopted it are looking at what's happening and examining it with a continuous quality improvement process. They're measuring what they're doing, making interventions, and remeasuring, and I think that makes all the difference."
The general consensus, though, is that more research is needed, ideally involving randomized clinical trials.
"I still believe some intermittent positive-pressure ventilation is needed to optimize forward blood flow," says Aufderheide, "but the final jury's not in yet. We need more research on this topic, particularly for professional rescuers."
"Even Dr. Ewy has called for the need for a randomized clinical trial," notes Eisenberg. "I would echo those sentiments."
The Pros and Cons of CCC CPR
Top docs will debate and discuss continuous chest compression CPR at the Emergency Cardiovascular Care Update 2008 conference this month in Las Vegas. Gordon Ewy, MD, will represent the "pro" side; his arguments are outlined in the article on page 41. His opponent will be Tom Rea, MD, MPH, medical program director for the Center for the Evaluation of Emergency Medical Services, a collaborative venture of King County (WA) EMS and the University of Washington. Rea urges caution in changing CPR, believing more research is needed. "We really do not know which [method] is better, and the current state of the evidence is insufficient, so we're forced to make an educated guess," he says. "Dr. Ewy's educated guess is reasonable but far from definitive. My position is that we need to acknowledge the information we use to make these decisions is very slim as it stands, and I hope the leadership promoting one or another type of CPR makes it clear that we do not have a level of evidence that should make us very confident that we know exactly what is right. We need to work to accrue high-quality information that will help us to address these controversies." For more, see www.citizencpr.org.
