RESUMO
The study was undertaken to clarify the hemodynamic effects of intermittent positive pressure ventilation (IPPV) and intermittent mandatory ventilation (IMV) with variation of the positive end-expiratory pressure (PEEP) from 5 to 15 mbar. The cardiac index (CI) was measured with thermodilation techniques in 30 infants who underwent open-heart surgery with extracorporeal circulation for various congenital heart lesions. The age of the patients varied from 6 to 28 months and body weight from 4 to 15 kg. During IPPV the changing of PEEP levels up to 5 mbar did not have any effect on Cl. Further increase in the PEEP to 10 and 15 mbar caused a significant decrease in Cl (from 2.6 to 2.0 l.min-1.m-2, p less than 0.05). The oxygen consumption (VO2) did not change significantly (135 ml.min-1.m-2 to 128 l.min-1.m-2, p greater than 0.5). A positive end-expiratory pressure exceeding 5 mbar caused a decrease of intrapulmonary veno-arterial blood shunting (QS/QT) from 12.3 to 7.1%; p less than 0.01), while PEEP at the level of 5 mbar did not affect this parameter. The alveolo-arterial oxygen gradient (AsDO2) also decreased from 182 to 135 torr (p less than 0.01) when PEEP was 10 and 15 mbar.(ABSTRACT TRUNCATED AT 250 WORDS)
