[An experimental study of the influence of positive end-expiratory pressure for a bidirectional cavopulmonary shunt].

In 8 mongrel dogs (weight 9-13 kg), we created a bidirectional cavopulmonary shunt through 4th intercostal thoracotomy. Positive end-expiratory pressure (PEEP) was added from 0cmH2O to 16cmH2O at the steps of 2cmH2O. The heart rate (HR), central venous pressure (CVP), pulmonary artery pressure (PAP), femoral artery pressure (FAP), pulmonary vascular resistance index (PVRI), and systemic vascular resistance index (SVRI) were measured as parameters of hemodynamics. Cardiac output (CO), pulmonary artery flow at proximal and distal site of this shunt (D-SF, P-SF) were measured using a magnetic flow meter. Blood gas analysis (PH, PaO2, PaCO2, HCO3-) were performed at the same time. HR had no significant change. CVP, PAP, PVRI, SVRI increased significantly (p less than 0.05, p less than 0.05, p less than 0.05, p less than 0.05) at 2cmH2O (9.2 +/- 2.5 mmHg), 10cmH2O), (29.3 +/- 5.5 mmHg), 4cmH2O (287 +2- 56 dyne.sec.cm-5.m2), and 8cmH2O (1298 +/- 156 dyne.sec.cm-5.m2) compared with 0cmH2O (87.3 +/- 2.6 mmHg, 26.8 +/- 3.4 mmHg, 240 +/- 29 dyne.sec.cm-5.m2, 1136 +/- 176 dyne.sec.cm-5.m2). FAP, CO, D-SF, P-SF decreased significantly (p less than 0.01, p less than 0.05, p less than 0.01, p less than 0.05) at 6cmH2O (129 +/- 7 mmHg), 2cmH2O(0.44 +/- 0.05 L/min), 2cmH2O(449 +/- 47 ml/min), and 8cmH2O(105 +/- 17 ml/min) compared with 0cmH2O(148 +/- 11 mmHg, 048 +/- 0.06 L/min, 471 +/- 44 ml/min, 132 +/- 19 ml/min). On blood gas analysis, PaO2 increased significantly (p less than 0.05) from 2cmH2O PEEP except PH, PaCO2, HCO3-. A mechanism for decline in D-SF was considered of being a secondary effect due to increase in CVP.(ABSTRACT TRUNCATED AT 250 WORDS)