effect of lung recruitment after cardiac surgery of morbidly obese patients.

Lung atelectasis is frequently observed after open heart surgery. It may lead to hypoxemia, increased shunt fraction, and pulmonary complications in the postoperative period. Also during general anesthesia, as well as during the immediate postoperative period, obese patient are more likely than non obese patients to develop atelectasis. After cardiac surgery, patients are transfered in intensive care unit. Patients are ventilated with volume controlled ventilation by MAQUET Servo i respirator which consisted of a tidal volume of 6-8 ml/kg and a positive end-expiratory pressure (PEEP) is applied at 5 cmH2O. PEEP is a pressure who is maintained within the airways during expiration at each expiratory cycle. It can be titrated from 0 to 20 cmH2O. This mechanical ventilation setting prevents the alveolar collapse formation at the end of expiration. The positive expiratory pressure also increases the time during which the gas exchange between alveolus and capillary occur. Sustainable maintenance of alveolar opening prevents the atelectasis formation. Also, in cardiac surgery and morbidly obese patients, recruitment maneuvers improves oxygenation. The main objective of the study is to evaluate the effect of maneuver recruitment and increasing PEEP on the incidence of respiratory distress after weaning from mechanical ventilation in obese patients after cardiac surgery. We chose to carry out the recruitment maneuver using pressure controlled ventilation (i MAQUET Servo ventilator) with inspiratory pressure at 30 cmH2O and PEEP at 15 cmH2O during 4 minutes In the hour following admission to intensive care, patients are randomized into 3 groups: 1/lack of recruitment maneuver and maintaining the initial ventilation (control group) 2/recruitment maneuver (RM) is applied with controlled pressure ventilation for 4 minutes then recovery to the initial ventilation. 5 cmH2O PEEP is continued during the mechanical ventilation with volume controlled ventilation after RM. 3/ recruitment maneuver is applied with controlled pressure ventilation for 4 minutes then recovery to the initial ventilation. 10 cmH2O is continued during the mechanical ventilation with volume controlled ventilation after RM. recruitment maneuver is carried out immediatly after randomisation.