Abstract

The children who received. open heart surgery were mechanically ventilated with Bear 2 volume ventilator postoperatively in pediatric intensive care unit. To clarify the relationship of inspiratory: expiratory ratio to optimum ventilation and oxygenation, all the patients were ventilated at I: E ratios of 1: 2, 1: 1 and 2: 1, at random order, while peak inspiratory pressure, tidal volume and respiratory frequency remained constant. The results showed that the use of a long inspiratory phase resulted in increased PaO2 and decreased alveolar-arterial oxygen difference, indicating improvement in oxygenation, but PaCO2 and dead space(VD/VT) didn't show any changes, indicating no effects on pulmonary ventilation.