Changes in pulmonary mechanics during laparoscopic gastroplasty in morbidly obese patients

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.

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.

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 O2 saturation. Respiratory system compliance and pulmonary insufflation pressures returned to baseline values after abdominal deflation.

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.