Does Pulmonary Compliance Optimization Through PEEP Manipulations Reduces the Incidence of Postoperative Hypoxaemia in Bariatric Surgery?

Detailed Summary

General anesthesia, even in patients in good health, impairs gas exchanges and ventilatory mechanics. These effects result primarily from atelectasis formation. They occur in 85-90% of healthy patients in the minutes following the induction when a positive end expiratory pressure (PEEP) is not used. The functional residual capacity (FRC) of obese patients during general anesthesia is even smaller than the one of healthy patients. There is a direct relationship between the body mass index and the decrease of the functional residual capacity. Obese patients have therefore more atelectasis. The increased abdominal pressure during the pneumoperitoneum will increase the decrease of the CRF, and thus aggravate the formation of these atelectasis. Atelectasis affect the peroperative gas exchanges and are likely to be involved in the worsening of postoperative hypoxemia episodes. In addition, atelectasis alter the clearance of secretions and the lymph flow, which predispose to lung infections.Taking all these factors into account, it is logical to think that the atelectasis presence can lead to an increase of the postsurgical morbidity (respiratory distress, infections). That is why actively fighting against the formation of these atelectasis is important. There is a lack of scientific evidence to say that the strategies against atelectasis as PEEP have a significant impact on the patient's postoperative status. The expected clinical benefits balance (reduction of respiratory distress episodes, infections and mortality) versus the risks linked to the maneuvers done to reduce the development of atelectasis (barotraumas, cardiac complications) remains to be determined. The primary goal of this study is to evaluate the impact of two different alveolar recruitment strategies on the incidence of postoperative hypoxemia in obese patients after bariatric surgery. The secondary objectives of this study are to compare the number of recruitment maneuvers, the Pa02 / FI02 ratio (ratio of arterial oxygen partial pressure to fractional inspired oxygen), the dynamic compliance, the anatomic dead space and intraoperative PaCO2-EtCO2 gradient (arterial and end tidal gradient) between two alveolar recruitment strategies applied in obese patients during laparoscopic bariatric surgery (gastric bypass or sleeve gastrectomy). The tertiary objectives of this study are to report the number of respiratory complications and postoperative wound infections at the 30th postoperative day.

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