Friday, December 21, 2007

CPR Meets Evidence-Based Medicine Revisited

Big changes are brewing. Two articles were published in the most recent issue of Circulation. Both tend to support the notion that Continuous Chest Compression Cardiopulmonary Rescusitation (CCC CPR) using chest compressions only may be as effective as using both chest compressions and breathing.

Read more about why this is important here.
Big changes are brewing. Two articles were just published in Circulation (here and here). Both tend to support the notion that Continuous Chest Compression Cardiopulmonary Rescusitation (CCC CPR) using chest compressions only may be as effective as with both chest compressions and breathing.

I wrote about Dr. Gordon Ewy's long struggle to convince the medical community of this possibility several years ago. I'm impressed that it looks like he may be vindicated.

CPR done immediately, prior to the arrival of paramedics, and by trained lay people has the potential for saving many lives and even for preventing the terrible consequences of cardiac arrest those who survive. The standard protocol (for adults) is to give the patient two breaths and then thirty chest compressions then alternating back and forth. The question is whether this is the best way. There is now increasing evidence that it is not.

Ewy, who wrote a previous review article on the subject was struck some years ago by a fascinating observation. A woman was attempting to resuscitate her husband using CPR as coached by an emergency
"Why is it that every time I press on his chest he opens his eyes, and every time I stop to breathe for him he goes back to sleep?"
This phenomenon has also been noted by previously by paramedics and among other things, caused Ewy to speculate that perhaps the breathing part of CPR isn't that important. Moreover, he questioned whether it was in fact harmful given that it prevented chest compressions from being done continuously.

Animal studies had suggested that the oxygenation during the breathing phase was not nearly as important as maintaining perfusion which only happens during chest compressions. In fact, it takes some "momentum" to maintain that perfusion which is lost when they are not done continuously.

The two studies linked above were observational studies but the first demonstrated that outcomes were similar in one month regardless of which type of CPR was done in the field (over 11,000 patients). The second showed that neurological outcome a year post-event was similar for the CCC CPR vs. conventional CPR.

For prolonged cases (resuscitations greater than 15 minutes), the second study showed a slight advantage for conventional CPR. This may represent what statisticians refer to as an alpha-error though (also known as a fake finding due to bad luck). The reason I say that is that even no CPR did better in those patients which to me doesn't make biological sense.

The big question and one that Ewy himself raises in the accompanying editorial, is whether there is now enough data to warrant a change in the general CPR guidelines given to perhaps millions of lay people worldwide eliminating the breathing portion. Certainly both of these new studies have enough holes in them to drive a semi through; but whether writing new guidelines on this issue has enormous implications for a simple reason.

One of the biggest barriers to people performing CPR on strangers is the "mouth-to-mouth" part. One survey Ewy did in the past showed that only 15% of lay people would be willing to do this. Eliminating this requirement could cause many people who would otherwise walk away to actually be willing to do CCC CPR. The public health consequences of such a change could be extraordinary.

The question is now becoming not so much whether there's enough evidence to recommend the change but rather whether there's enough evidence to continue teaching what may be a futile, deleterious practice.

Again, see my previous post for more information about this.

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