Abstract:

Objective To investigate the effects of different ventilation modes during cardiopulmonary bypass on pulmonary function after cardiac surgery. Methods Forty patients undergoing surgery for aortic valve diseases were selected, and were randomly divided into groupⅠ(0 of tidal volume and 0 of positive end expiratory pressure), groupⅡ (5 mL/kg of tidal volume and 0 of positive end expiratory pressure), group Ⅲ (0 of tidal volume and 10 cmH₂O of positive end expiratory pressure) and group Ⅳ(5 mL/kg of tidal volume and 10 cmH₂O of positive end expiratory pressure) according to different ventilation modes during cardiopulmonary bypass, with 10 patients in each group. Pulmonary function and hemodynamics-related parameters were recorded before chest opening, after weaning from bypass, after chest closure and 4 h after cardiopulmonary bypass, including arterial oxygen pressure(PaO₂), alveolo-arterial oxygen partial pressure difference (AaDO₂), intrapulmonary shunt (Qs/Qt), peak inspiratory pressure (PIP), ratio of volume of dead space to tidal volume(Vd/Vt), lung dynamic compliance (Cdyn) and cardiac index(CI), and statistical analysis and comparison were conducted. Results Compared with parameters before chest opening, PaO₂ significantly decreased and CI significantly increased 4 h after cardiopulmonary bypass in each group (P<0.05), Qs/Qt, PIP and Vd/Vt significantly increased and Cdyn significantly decreased in groupⅠand groupⅡ(P<0.05), AaDO₂ significantly decreased in group Ⅲ and group Ⅳ (P<0.05). Compared with parameters in groupⅠand groupⅡ, PaO₂ and Cdyn significantly increased, and AaDO₂, Qs/Qt, PIP and Vd/Vt significantly decreased 4 h after cardiopulmonary bypass in group Ⅲ and group Ⅳ (P<0.05). Conclusion Compared with single mechanical ventilation, continuous positive airway pressure during cardiopulmonary bypass may significantly mitigate lung injury after cardiac surgery.

Key words: cardiopulmonary bypass, mechanical ventilation, continuous positive airway pressure, pulmonary function