The effects of positive end-expiratory pressure during active compression decompression cardiopulmonary resuscitation with the inspiratory threshold valve

The use of an inspiratory impedance threshold valve (ITV) during active com pression-decompression (ACD) cardiopulmonary resuscitation (CPR) improves p erfusion pressures, and vital organ blood flow. We Evaluated the effects of positive end-expiratory pressure (PEEP) on gas exchange, and coronary perf usion pressure gradients during ACD + ITV CPR in a porcine cardiac arrest m odel. All animals received pure oxygen intermittent positive pressure venti lation (IPPV) at a 5:1 compression-ventilation ratio during ACD + ITV CPR. After 8 min, pigs were randomized to further IPPV alone (n = 8), or IPPV wi th increasing levels of PEEP (n = 8) of 2.5, 5.0, 7.5, and 10 cm H2O for 4 consecutive min each, respectively. Mean +/- SEM arterial oxygen partial pr essure decreased in the IPPV group from 150 +/- 30 at baseline after 8 min of CPR to 110 +/- 25 torr at 24 min, but increased in the PEEP group from 1 15 +/- 15 to 170 +/- 25 torr with increasing levels of PEEP (P <0.02 for co mparisons within groups). Mean <plus/minus> SEM diastolic aortic minus dias tolic left ventricular pressure gradient was significantly (P < 0.001) high er after the administration of PEEP (24 <plus/minus> 0 vs 17 +/- 1 mmHg wit h 5 cm H2O of PEEP, and 26 +/- 0 vs 17 +/- 1 mm Hg with 10 cm H2O of PEEP), whereas the diastolic aortic minus right atrial pressure gradient (coronar y perfusion pressure) was comparable between groups. Furthermore, systolic aortic pressures were significantly (P < 0.05) higher with 10 cm H2O of PEE P when compared with IPPV alone (68 <plus/minus> 0 vs 59 +/- 2 mm Hg). In c onclusion, when CPR was performed with devices designed to improve venous r eturn to the chest, increasing PEEP levels improved oxygenation. Moreover, PEEP significantly increased the diastolic aortic minus left ventricular gr adient and did not affect the decompression phase aortic minus right atrial pressure gradient. These data suggest that PEEP reduces alveolar collapse during ACD + ITV CPR, thus leading to an increase in indirect myocardial co mpression.