To improve the efficiency of standard cardiopulmonary resuscitation (CPR), we evaluated the potential value of impeding respiratory gas exchange selectively during the decompression phase of standard CPR in a porcine model of ventricular fibrillation. After 6 min of untreated cardiac arrest, anesthetized farm pigs weighing 30 kg were randomized to be treated with either standard CPR with a sham valve (n = 11) or standard CPR plus a functional inspiratory impedance threshold valve (ITV(TM)) (n = 11). Coronary perfusion pressure (CPP) (diastolic aortic minus right atrial pressure) was the primary endpoint. Vital organ blood flow was assessed with radiolabeled microspheres after 6 min of CPR, and defibrillation was attempted 11 min after starting CPR. After 2 min of CPR, mean +/- SEM CPP was 14 +/- 2 mm Hg with the sham valve versus 20 +/- 2 mm Hg in the ITV group (P < 0.006). Significantly higher CPPs were maintained throughout the study when the ITV was used. After 6 min of CPR, mean +/- SEM left ventricular and global cerebral blood flows were 0.10 +/- 0.03 and 0.19 +/- 0.03 mL. min(-1). g(-1) in the Control group versus 0.19 +/- 0.03 and 0.26 +/- 0.03 mL. min(-1). g(-1) in the ITV group, respectively (P < 0.05). Fifteen minutes after successful defibrillation, 2 of 11 animals were alive in the Control group versus 6 of 11 in the ITV group (not significant). In conclusion, use of an inspiratory impedance valve during standard CPR resulted in a marked increase in CPP and vital organ blood flow after 6 min of cardiac arrest.

Background-This study evaluated the potential for an inspiratory impedance threshold valve (ITV)

No abstract

These studies demonstrate that it is feasible to use a device that creates inspiratory impedance in spontaneously breathing normotensive and hypotensive pigs to increase blood pressure and enhance cardiopulmonary circulation in the absence of immediate fluid resuscitation. Further studies are needed to evaluate the potential long-term effects and limitations of this new approach to treat hypovolemic hypotension.