Compara??o entre ventila??o controlada a volume e a press?o no tratamento da hipoxemia no período pós-operatório de cirurgia de revasculariza??o do miocárdio

摘要

BACKGROUND AND OBJECTIVES: Pressure controlled ventilation (PCV) has been used as the ventilation mode of choice in coronary artery bypass graft surgery patients who develop severe hypoxemia in the immediate postoperative period. However, there are no evidences showing that pressure controlled ventilation is more effective in reversing postoperative hypoxemia than controlled mandatory ventilation (CMV). This study aimed at comparing the effects of both ventilation modes on systemic oxygenation in cardiac surgery patients who develop hypoxemia characterized by PaO2/FiO2 ratio lower than 200 in the immediate postoperative period. METHODS: Participated in this study 61 consecutive patients with PaO2/FiO2 ratio lower than 200 who were randomly allocated in two groups according to the ventilatory mode (CMV and PCV). Tidal volume, respiratory rate, inspiration/expiration ratio and positive end-expiratory pressure were kept constant throughout the study in both groups. PaO2/FiO2 ratio and pulmonary shunt were obtained 1 or 2 hours after ICU admission. RESULTS: A significant increase in PaO2/FiO2 ratio and a decrease in pulmonary shunt were observed in both groups one or two hours after mechanical ventilation. However, no differences were observed between both ventilatory modes. CONCLUSIONS: Both ventilatory modes were equally effective in reversing hypoxemia observed in the immediate cardiac surgery postoperative period. Results show that inspiratory flow patterns are not relevant in the treatment of post cardiac surgery hypoxemia.