Effects of Preoperative Respiratory Physical Therapy on Postoperative Respiratory Function in Morbidly Obese Patients Undergoing Bariatric Surgery. A Randomized, Controlled, Clinical Trial

Background. Morbidly obese patients show an increased risk of hypoxemia during the postoperative period resulting in a higher incidence of postoperative pulmonary complications and prolonged hospital length of stay when compared with normal weight subjects. Mechanisms involved in this predisposition of morbidly obese patients for develop this physiopathologic scheme include a greater impairment on the respiratory mechanics induced by general anesthesia and paralysis -greater reduction in pulmonary and chest compliances and higher airway resistance- and an increment in ventilatory requirements. That leads to an increased work of breathing (WOB) and oxygen consumption (VO2). These effects are exaggerated in patients undergoing laparoscopic surgery because the direct effects of the pneumoperitoneum on the pulmonary mechanics. In addition, in morbidly obese patients respiratory muscles show a reduction in both strength and endurance probably a cause of the fatty tissular infiltration and the exacerbated inflammatory response usually observed in these patients.

Respiratory physical therapy has shown to be effective and reduce postoperative pulmonary complications both, as postoperative treatment and when given preoperatively. When applied postoperatively respiratory physiotherapy has proved to be able to expand pulmonary volumes and to improve arterial oxygenation, leading to decreases in postoperative pulmonary complications, specially after abdominal surgery. In the specific setting of morbidly obese patients submitted to bariatric surgery, postoperative inspiratory muscle training (IMT ) improves inspiratory muscle strength and endurance allowing an earlier recovery of pulmonary airflows.

There are scanty data about the results of applying respiratory physiotherapy on the preoperative period. However it has proved to be able to reduce the postoperative incidence of postoperative pulmonary complications in some different settings: (1) In patients after thoracic surgery, (2) In patients undergoing CABG surgery, specially in those considered at high risk for pulmonary complications and (3) after upper abdominal surgery.

At our knowledge no studies aimed to determine wether preoperative respiratory physiotherapy could improve the postoperative respiratory function in morbidly obese patients have been published.

The objective of this study was to evaluate the effects of a preoperative respiratory physical therapy program on the postoperative respiratory function in morbidly obese patients undergoing bariatric laparoscopic surgery.