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(Circulation. 2002;105:124.)
© 2002 American Heart Association, Inc.

Basic Science Reports

Use of an Inspiratory Impedance Valve Improves Neurologically Intact Survival in a Porcine Model of Ventricular Fibrillation

Keith G. Lurie, MD; Todd Zielinski, MS; Scott McKnite, BS; Tom Aufderheide, MD; Wolfgang Voelckel, MD

From the Cardiac Arrhythmia Center, University of Minnesota, Minneapolis (K.G.L., T.Z., S.M., W.V.); the Department of Emergency Medicine, Medical College of Wisconsin, Milwaukee (T.A.); and the Department of Anesthesiology, Leopold-Franzens-University, Innsbruck, Austria (W.V.).

Correspondence to Keith G. Lurie, MD, Department of Medicine, University of Minnesota, MMC 508, AHC, 420 Delaware St SE, Minneapolis, MN 55455. E-mail klurie{at}resqcpr.com

Background— This study evaluated the potential for an inspiratory impedance threshold valve (ITV) to improve 24-hour survival and neurological function in a pig model of cardiac arrest.

Methods and Results— Using a randomized, prospective, and blinded design, we compared the effects of a sham versus active ITV on 24-hour survival and neurological function. After 6 minutes of ventricular fibrillation (VF), followed by 6 minutes of cardiopulmonary resuscitation (CPR) with either a sham or an active valve, anesthetized pigs received 3 sequential 200-J shocks. If VF persisted, they received epinephrine (0.045 mg/kg), 90 seconds of CPR, and 3 more 200-J shocks. A total of 11 of 20 pigs (55%) in the sham versus 17 of 20 (85%) in the active valve group survived for 24 hours (P<0.05). Neurological scores were significantly higher with the active valve; the cerebral performance score (1=normal, 5=brain death) was 2.2±0.2 with the sham ITV versus 1.4±0.2 with the active valve (P<0.05). A total of 1 of 11 in the sham versus 12 of 17 in the active valve group had completely normal neurological function (P<0.05). Peak end-tidal CO₂ (PETCO₂) values were significantly higher with the active valve (20.4±1.0) than the sham (16.8±1.5) (P<0.05). PETCO₂ >18 mm Hg correlated with increased survival (P<0.05).

Conclusions— Use of a functional ITV during standard CPR significantly improved 24-hour survival rates and neurological recovery. PETCO₂ and systolic blood pressure were also significantly higher in the active valve group. These data support further evaluation of ITV during standard CPR.

Key Words: cardiac arrest • fibrillation • cardiopulmonary resuscitation • valves • survival • arrhythmia • brain

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