Changes in pulmonary mechanics during laparoscopic gastroplasty in morbidly obese patients

Background: Obesity is an important respiratory risk factor after abdominal surgery. Laparoscopic surgical techniques seem beneficial in obese patients in terms of respiratory morbidity, with a faster return to normal respiratory function. However, there is little information about intraoperative respiratory mechanics and about patient tolerance to abdominal insufflation in the morbidly obese. Methods: We studied respiratory mechanics and arterial blood gases in 15 morbidly obese patients (mean BMI = 45) undergoing laparoscopic gastroplasty under general anaesthesia and controlled ventilation. Respiratory mechanics were analysed using side-stream spirometry. Results: When compared to preinsufflation values, servocontrolled abdominal insufflation to 2.26 kPa caused a significant decrease in respiratory system compliance (31%), a significant increase in peak (17%) and plateau (32%) airway pressures at constant tidal volume with a significant hypercapnia but no change in arterial O-2 saturation. Respiratory system compliance and pulmonary insufflation pressures returned to baseline values after abdominal deflation. Conclusion: These alterations in pulmonary mechanics are less than those observed with comparable degrees of abdominal inflation in non-obese patients, and were well tolerated. From the point of view of intraoperative respiratory mechanics, laparoscopic surgery is safe in morbidly obese patients.