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The Evolving Science and Guidelines of CPR

Pearl of wisdom for the day: If given the option, don’t let your heart stop.  Very Bad Things soon follow if your heart stops.

In spite of what the entertainment industry would have you believe, it is extremely difficult to save the life of someone in cardiac arrest.  A few random breaths, slow rocking chest compressions, even the ever-so-dramatic overhand blow to the chest accompanied by the scream “Don’t you die on me, dammit!” are unlikely to successfully resuscitate someone following an arrest, and even if it does, they won’t be in any shape to go chase Locke across the island with Jack and Kate five minutes later.

Even with properly performed CPR, started within seconds of an arrest, in a hospital with all the required expertise and support equipment, only roughly half survive their initial arrest event.  Even fewer (25-33%) survive to discharge from the hospital, and ~75% have a good neurologic outcome.  For arrests out of the hospital, where there can be huge delays in treatment, mere survival is significantly lower, often measured in the single digits.

The Limitations Of CPR

Why doesn’t CPR save more people?  Well, it really isn’t meant to; at least, not on its own.  Cardio-respiratory arrest is the common pathway of death, but it isn’t in itself a diagnosis.  The essential question to be answered is why someone stopped breathing, or why their heart stopped in the first place.  Unless you can answer that question and address the problem, even if CPR manages to restore a heartbeat it’s likely to stop again in short order.

It’s clearly unrealistic though to expect a random bystander to diagnose and treat another random stranger who happened to arrest in their vicinity.  The rescue breaths and chest compressions of CPR are therefore primarily designed to buy time, hopefully enough time to get to the EMTs and Emergency/Critical Care team whose job it is to figure out what caused the arrest in the first place and reverse it before permanent damage is done.

In spite of the availability of public CPR training courses and the widespread knowledge of the existence of CPR, most people remain untrained, and the vast majority of those who have been trained (even medical personnel) rarely have cause to think about the skill, much less practice it.  The result is that complete novices in CPR are the first responders to the overwhelming majority of arrests.  Should we be surprised, then, that in no more than half of all arrests is any CPR provided by bystanders, and that the quality of CPR when it is given is often sub-par?

I don’t mean that as an indictment of innocent bystanders of an arrest.  Simply witnessing an arrest is traumatic enough; to be in such a situation and asked to recognize the emergency, remember distant and somewhat arcane training, to have the initiative and courage to step forward and act, and to do so quickly and effectively is an immense amount to expect from anyone.  Nevertheless, if the goal is to reduce the amount of time a victim of an arrest is without circulation, we needed to find some way to enable more people to provide quality CPR.

K.I.S.S.

The desire to reduce these impediments to good CPR delivery, combined with improved understanding of the physiology of people during arrests and CPR, led the American Heart Association (AHA) to make some significant revisions to its CPR guidelines in 2005.  The revised guidelines were notably more streamlined, focusing less on tools, drugs, and advanced skills used by professionals, and even reducing the emphasis of breathing to focus instead on simply maintaining circulation of blood.  Instead of a variety of age stratified ratios of compressions to rescue breaths, the AHA began to teach a single universal guideline for single bystander CPR: 30 compressions at a rate of 100/minute, then 2 breaths, then repeat until either help arrives or the person is breathing on their own.  Compared to the prior CPR guidelines, it was simpler, easier to remember, and easier to execute.

In 2008 this was simplified even further.  For adult cardiac arrests, it was demonstrated that “compression-only” or “hands-only” CPR was equally effective to CPR using both compressions and rescue breathing, yet was simpler, even easier to remember, had fewer interruptions, and eliminated the aversion to mouth-to-mouth that some people experience.  All of this is thought to make people more likely to intervene and provide quality CPR, improving the odds of a dire situation.

Though it may seem counterintuitive not to provide rescue breaths for someone in cardio-respiratory arrest, the rationale is solid.  “Deoxygenated” or venous blood still has a good amount of oxygen in it (usually about 75% of oxygenated blood), and it carries a lot more than just oxygen.  The blood content of the nutrients that cells require is largely the same no matter whether the blood has been oxygenated or not, and blood flow also removes harmful metabolic byproducts that build up rapidly in its absence.  Though breathing is necessary in the long run, but you can get by without breathing a lot longer than you can survive without blood flow.

Studies have confirmed that “compression-only” and conventional CPR are equally efficacious in adult cardiac arrests, and that the “compression-only” method is easier to learn and remember.  By reducing the complexity of CPR to something that essentially fits on a bumper sticker, we are likely to improve the overall odds for adults who arrest out of the hospital.

…But Maybe Not That Simple

Have we made it too simple though?  Children arrest too, but for very different reasons than adults.  Most kids suffer respiratory arrests that then cause cardiac arrest, not primary cardiac arrests like most adults.  Eliminating rescue breathing from childhood resuscitations could in fact result in worse outcomes.  The AHA and medical community at large are aware of this, which is why the “compressions-only” CPR has not been recommended for children.  Even so, it is likely that in advocating for “compression-only” CPR to benefit adults, some children will inadvertently be subjected to sub-optimal CPR.

A new study out of Japan and published last month in The Lancet provides some sobering but powerful information that may guide future CPR guidelines.  The investigators examined all arrests of children over a 3-year span in Japan, documenting the type of arrest, presence and type of CPR, and short and long-term outcomes among other measures.

Out of 5158 childhood arrests, 2719 (53%) had no CPR attempted by anyone prior to EMS arrival.  Survival rates were abysmally poor without CPR at ~7% alive one month after arrest.  Though still depressingly low, CPR significantly improved survival to ~11%.  Of equal importance, those above 1 year of age who did get CPR, any type of CPR, also had markedly better odds of having favorable neurologic function at one month from the arrest.  As with the adult experience, an arrest out of the hospital is a dire situation, but any type of CPR is better than nothing, and can have a marked improvement in the (unfortunately small) likelihood of having a positive outcome.

The concern I had, however, was whether inappropriate “compression-only” CPR was inferior to conventional CPR with both compressions and rescue breaths, and whether we need to keep this in mind when designing our CPR program for the public.  The authors of this study were able to make just such a comparison.  Both forms of CPR were equally effective when the arrest had a cardiac origin, just as we’ve seen in adults.  However, as suspected, victims of arrests of a non-cardiac origin provided “compressions-only” CPR did no better than those given no CPR; only the combination of compressions and rescue breathing affected a significant benefit.

Furthermore, of the 2,439 children who did receive CPR, 36% received “compression-only” CPR.  Since 71% of all of the arrests in this study were non-cardiac in origin, this means that 25% of the CPR administered was inappropriate and ineffective.

Clearly, this study has limitations in being observational in design, and there are obvious issues generalizing from the Japanese population to that of the US, among other smaller concerns.  Nevertheless, this study provides a few important lessons to be considered.

First, it shines the harsh light of reality on the overly optimistic expectations of CPR sometimes provided but the news media and frequently by the entertainment industry.

Second, it demonstrates the efficacy of CPR in improving both survival and the quality of outcomes from out of hospital arrests, and the potential benefits of further enabling the public to perform appropriate CPR.

Third, it reinforces the decision of the AHA to restrict “compression-only” CPR to adults with suspected cardiac arrest, and not to apply it to children.

Finally, it seems to validate my concern that the introduction of “compression-only” CPR may be detrimental to the pediatric population.  Recall that the two CPR techniques were equally efficacious in adults (and apparently children) with an arrest of cardiac origin.  The AHA has therefore assumed that there was no detriment to the further simplification of the CPR guidelines, while yeilding a theoretical benefit derived from better quality of compressions and a greater percentage of bystanders willing and able to provide CPR.  If, however, “compression-only” CPR is only equal to conventional CPR in the adult population yet generates a negative impact on the quality of CPR provided to children, the AHA may choose to reconsider the wisdom of advocating “compression-only” CPR.  Obviously, this is still an open question, and further studies are needed (and are currently being performed), but I am curious how this information may affect the new guidelines due for release late 2010.

We will continue to refine the CPR guidelines to improve the outcomes from out of hospital arrests using the best available science, but the largest area for improvement is in the number of people in the community trained and willing to perform basic CPR.  It’s cheap, it’s easy, and the classes are actually fun.  Though you will hopefully never use the skill, you have the ability to help save a life.  Please, if you are at all inclined, get CPR certified.

Posted in: Science and Medicine

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