This transcript has been edited for clarity.
Robert D. Glatter, MD: Welcome. I’m Dr Robert Glatter, medical adviser for Medscape Emergency Medicine. with a remarkable increase in neurologically intact survival. Welcome, gentlemen.
Dr. Pepe, I’d like to start off by thanking you for taking time to join us to discuss this novel concept of head-up or what you now refer to as a neuroprotective cardiopulmonary resuscitation (CPR) bundle. Can you define what this entails and why it is referred to as a neuroprotective CPR bundle?
Paul E. Pepe, MD, MPH: CPR has been life saving for 60 years the way we’ve performed it, but probably only in a very small percentage of cases. That’s one of the problems. We have almost a thousand people a day who have sudden cardiac arrest out in the community alone and more in the hospital.
We know that early defibrillation and early CPR can contribute, but it’s still a small percentage of those. About 75%-85% of the cases that we go out to see will have nonshockable rhythms and flatlines. Some cases are what we call “pulseless electrical activity,” meaning that it looks like there is some kind of organized complex, but there is no pulse associated with it.
That’s why it’s a problem, because they don’t come back. Part of the reason why we see poor outcomes is not only that these cases tend to be people who, say, were in ventricular fibrillation and then just went on over time and were not witnessed or resuscitated or had a long response time. They basically either go into flatline or autoconvert into these bizarre rhythms.
The other issue is the way we perform CPR. CPR has been lifesaving, but it only generates about 20% and maybe 15% in some cases of normal blood flow, and particularly, cerebral perfusion pressure. We’ve looked at this nicely in the laboratory.
For example, during chest compressions, we’re hoping during the recoil phase to pull blood down and back into the right heart. The problem is that you’re not only setting a pressure rate up here to the arterial side but also, you’re setting back pressure wave on the venous side. Obviously, the arterial side always wins out, but it’s just not as efficient as it could be, at 20% or 30%.
What does this entail? It entails several independent mechanisms in terms of how they work, but they all do the same thing, which is they help to pull blood out of the brain and back into the right heart by basically manipulating intrathoracic pressure and creating more of a vacuum to get blood back there.
It’s so important that people do quality CPR. You have to have a good release and that helps us suck a little bit of blood and sucks the air in. As soon as the air rushes in, it neutralizes the pressure and there’s no more vacuum and nothing else is happening until the next squeeze.
What we have found is that we can cap the airway just for a second with a little pop-up valve. It acts like when you’re sucking a milkshake through a straw and it creates more of a vacuum in the chest. Just a little pop-up valve that pulls a little bit more blood out of the brain and the rest of the body and into the right heart.
We’ve shown in a human study that, for example, the systolic blood pressure almost doubles. It really goes from 40 mm Hg during standard CPR up to 80 mm Hg, and that would be sustained for 14-15 minutes. That was a nice little study that was done in Milwaukee a few years ago.
The other thing that happens is, if you add on something else, it’s like a toilet plunger. I think many people have seen it; it’s called “active compression-decompression.” It not only compresses, but it decompresses. Where it becomes even more effective is that if you had broken bones or stiff bones as you get older or whatever it may be, as you do the CPR, you’re still getting the push down and then you’re getting the pull out. It helps on several levels. More importantly, when you put the two together, they’re very synergistic.
We, have already done the clinical trial that is the proof of concept, and that was published in The Lancet about 10 years ago. In that study, we found that the combination of those two dramatically improved survival rates by 50%, with 1-year survival neurologically intact. That got us on the right track.
The interesting thing is that someone said, “Can we lift the head up a little bit?” We did a large amount of work in the laboratory over 10 years, fine tuning it. When do you first lift the head? How soon is too soon? It’s probably bad if you just go right to it.
We had to get the pump primed a little bit with these other things to get the flow going better, not only pulling blood out of the brain but now, you have a better flow this way. You have to prime at first for a couple of minutes, and we worked out the timing: Is it 3 or 4 minutes? It seems the timing is right at about 2 minutes, then you gradually elevate the head over about 2 minutes. We’re finding that seems to be the optimal way to do it. About 2 minutes of priming with those other two devices, the adjuncts, and then gradually elevate the head over 2 minutes.
When we do that in the laboratory, we’re getting normalized cerebral perfusion pressures. You’re normalizing the flow back again with that. We’re seeing profound differences in outcome as a result, even in these cases of the nonshockables.