Improving standard cardiopulmonary resuscitation with an inspiratory impedance threshold valve in a porcine model of cardiac arrest

To improve the efficiency of standard cardiopulmonary resuscitation (CPR), we evaluated the potential value of impeding respiratory gas exchange selec tively during the decompression phase of standard CPR in a porcine model of ventricular fibrillation. After 6 min of untreated cardiac arrest, anesthe tized farm pigs weighing 30 kg were randomized to be treated with either st andard CPR with a sham valve (n = 11) or standard CPR plus a functional ins piratory impedance threshold valve (ITV (TM)) (n = 11). Coronary perfusion pressure (CPP) (diastolic aortic minus right atrial pressure) was the prima ry endpoint. Vital organ blood flow was assessed with radiolabeled microsph eres after 6 min of CPR, and defibrillation was attempted 11 min after star ting 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). Significantl y higher CPPs were maintained throughout the study when the ITV was used. A fter 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 Co ntrol 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 successfu l 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 inspirat ory impedance valve during standard CPR resulted in a marked increase in CP P and vital or-an blood flow after 6 min of cardiac arrest.