ResQ-Valve Improves Cardiac Arrest Survival Rate

Up to twice as many patients with a type of cardiac arrest called pulseless electrical activity survive long enough to get to a hospital intensive care unit when a simple device called a ResQ-Valve is used by emergency medical teams during cardio-pulmonary resuscitation (CPR), according to research conducted by the Department of Emergency Medicine at Froedtert & The Medical College of Wisconsin.

"In the process of studying this device, we did two things," said Tom P. Aufderheide, MD, FACEP, Medical College Professor of Emergency Medicine. "One is we determined the health benefits of its use during CPR. And, we coincidentally discovered significant issues surrounding the quality of CPR delivered at the scene of cardiac arrest. They're separate issues discovered in the same trial, one intentionally and one unintentionally. Both are very, very important, and as it turns out, physiologically related.

"The ResQ-Valve device can be placed on any airway, a facemask or an advanced airway such as an endotracheal tube. When CPR for cardiac arrest is performed, the device allows air to go out of the lungs when you push down on the chest. However, on the 'upstroke' of CPR as the chest returns to its normal position, the device does not let air into the lungs.

"An analogy would be like opening up a bellows with your hand over the nozzle of the bellows. It produces a suction inside the chest on the upstroke of CPR. The suction inside the chest on the upstroke pulls blood back from the abdomen and the legs back to the heart, so that when you push down again more blood is pumped out of the chest to the rest of the vital organs."

Time-to-CPR is Key to Survival
Cardiac arrest is a highly critical medical emergency. The outlook for cardiac arrest victims is terrible, because when the heart stops beating and instead just fibrillates (quivering instead of pumping) it can take just a few minutes for reduced blood flow to deny oxygen to vital organs. Brain damage and death are the most common outcomes of cardiac arrest, which strikes about 500,000 people in the US each year.

CPR is used to keep oxygen flowing while trying to get the heart to resume pumping to limit organ damage and ward off death long enough to get the patient to a hospital, where immediate intensive care can improve prospects for long-term survival.

"In effect, the device improves hemodynamics, or blood flow, during CPR," said Dr. Aufderheide. "In our study we did two things. First we did a small sub-study of 22 patients in which we actually inserted a femoral arterial blood pressure line at the scene of cardiac arrest and monitored blood pressure with the device. The devices were manufactured so that half of them were sham valves and just acted like a hollow conduit, and the other half were active valves performing the function of producing suction on the upstroke of CPR.

"Neither the treating paramedics nor our research team knew which device was which, and we monitored blood pressure. The second thing we did was a much larger study - 230 patients - and the primary endpoint of that study was ICU admission rate. We looked at how many patients lived from cardiac arrest and survived to be admitted to the intensive care unit."

Blood Pressure Doubled with Valve
The study was conducted through the Milwaukee County EMS system and patients were received by thirteen hospitals in Milwaukee. An abstract of the research involving the larger group of patients received the 2004 Best Critical Care Abstract Award from the American Heart Association. Dr. Aufderheide led the research team along with Dr. Ronald G. Pirrallo, MHSA, FACEP. Both physicians practice at the Froedtert & The Medical College emergency department. Other research team members included Keith Lurie, MD, of the University of Minnesota, and Terry Provo, BA, EMT-P, of Advanced Circulatory Systems in Minnesota.

"What we found first of all was that this device doubled blood pressure during CPR," said Dr. Aufderheide. The average systolic blood pressures were around 45 with the sham valve and were about 85 with the active ResQ-Valve.

"There were trends toward improved survival rates in all cardiac arrests, but statistically significant improved survival in a particular kind of cardiac arrest called pulseless electrical activity. It more than doubled survival rates in that patient population. So we've demonstrated in a single study that the device does what it's expected to do. By creating suction on the upstroke of CPR it pulls more blood back to the heart and doubles blood flow to vital organs, and that is translated into improved survival."

At the time of the study the ResQ-Valve was for investigational use only, said Dr. Aufderheide. "It is not used for standard care in our EMS system yet," he said. "We will be doing the definitive study next, beginning around late Fall 2005. That again will be funded by the National Institutes of Health, through the National Heart, Lung and Blood Institute, utilizing a consortium of clinical research centers called the Resuscitation Outcomes Consortium.

"These are ten sites similar to Milwaukee, with EMS systems, and we will manufacture sham and active valves. The primary endpoint of that study will be hospital discharge. We expect between about 9,000 and 10,000 patients. If that study is positive and demonstrates significantly improved survival to hospital discharge, we would expect the device to then be approved for standard clinical use and to be widely applied."

The Toilet Plunger Principle
Dr. Lurie began exploring the general principles behind ResQ-Valve after a real-life cardiac arrest incident involving a toilet plunger came his way. "It's an interesting story about how this came to be," said Dr. Aufderheide. "A father arrested at home and his young son found him on the bathroom floor in cardiac arrest on his back. The son took a toilet plunger and started plunging on his chest while Mom called for 9-1-1.

"The father was resuscitated and Dr. Lurie took care of this patient. He talked to the son, and the son said something very peculiar: 'You know, I kept using this toilet plunger on my father and he would open up his eyes and look at me, so I thought he was resuscitated so I'd stop. When I stopped, he would go unconscious again so I'd continue using the toilet plunger.'

"So Dr. Lurie developed a device called active compression-decompression CPR, which is essentially modeled on a toilet plunger. You push down and then pull up to hyperextend the chest, again on the upstroke of CPR where there's some normal negative pressure or small suction in the chest. As it turns out, this device is effective even without a ResQ-Valve."

The US Food and Drug Administration recently approved a newer version of the ResQ-Valve, called the ResQPOD, for use in patients with low blood pressure, Dr. Aufderheide said. He estimated the cost of each unit at under $100 and is hopeful that cost will not prohibit emergency medical systems from using it if it is approved for more general use. No increased incidents of complications were seen in either initial study group, and there were no reports from paramedics that using ResQ-Valve inhibited their work.

"We're very excited about this technology. It demonstrates that this fundamental physiologic principle of suction in the chest pulling blood back to the heart and increasing output on the chest compression is in fact a fundamental principle of patients in shock, such as patients in cardiac arrest. We're estimating, based on our research and our initial study, that this should increase survival to hospital discharge by 50%."

Other Research on CPR Techniques
Dr. Aufderheide and others at the Medical College have moved forward with the "coincidental" discoveries from the ResQ-Valve studies on other fronts. They've found that standard CPR techniques used by paramedics in the field often result in delivering too many breaths to patients per minute, making it difficult to generate the critical "negative pressure" in the chest.

This research has led to the development of a timing device that helps paramedics keep the breathing rate at optimal levels. How fingers and hands are placed on the chest by those conducting CPR is also being studied to find the best techniques for "hands-off" decompression that allows the chest to open as fully as possible on the upstroke.

"We went to the animal lab and reproduced clinically what we saw in the field in an animal model to determine whether excessive ventilation rates causing very high positive pressure in the chest inhibited venous blood return and compromised forward blood flow," said Dr. Aufderheide." In fact, that's exactly what happened. At 12 breaths a minute, six of seven pigs survived. At 30 breaths a minute, which is the average of what we saw in our study (in the field with humans), six of seven pigs died and the blood pressure during CPR plummeted.

"This was very important because until now no one had recognized that there was any consequence to excessive ventilation rates. Most current EMS educational materials stress establishing an airway and breathing for the patient, and health care providers have an innate response to breathe excessively for patients, because they're not breathing. Until now, there was no known consequence to breathing rapidly. Now we know that it significantly compromises forward blood flow during CPR and can be fatal. As a result, educational training is now being changed and the ventilation rates are being very carefully monitored, at least in our EMS system."

Dan Ullrich
HealthLink Contributing Writer