Evaluation of respiratory functions in morbid obesity during laparoscopic and open surgery: a comparative study

ABSTRACT

Thirty morbidly obese patients, with body mass index [BMI] >40 kg/m2, ASA physical status II and III, were randomly divided into two equal groups, 15 patients each GI [n = 15] was scheduled for laparoscopic surgery and GII [n = 15] was scheduled for open upper abdominal surgery. Their preoperative pulmonary function tests showed the following averages FVC 85.10% +/- 3.21%, FEV1s 83.12% +/- 6.08% and FEF 25-75 was 88.76% +/- 7.22% of the normal predicated values [S0]. The spirometric data were repeated after 24 hr [S24] and 72 hr [S72]. Blood gas measurements during spontaneous respiration at room air before surgical intervention including an arterial oxygen tension [PaO2] of 76.49 +/- 7.64 mmHg, arterial carbon dioxide tension [PaCO2] of 37.73 +/- 2.04 and pH of 7.40 +/- 0.02. All measurements were performed with the patient in supine position at five time points. The measurements were arterial blood gases [ABG], alveolar-arterial oxygen difference calculated as an index of pulmonary shunt and arterial to end-tidal CO2 tension difference [delta P] calculated as an index of physiological dead space. The lung/chest wall compliance as well as the maximal and minimal resistance of the total respiratory system were investigated. In GI [laparoscopy], PaCO2, ETCO2, P [A-a] O2, alveolar-arterial oxygen difference and arterial to end-tidal CO2 tension difference and resistance showed a significant rise after CO2 peritoneal insufflation. All measurements returned to normal values by the end of surgery. In GII [open surgery], those measurements did not show any considerable change. The postoperative pulmonary functions showed a marked reduction in both groups but to a lesser degree in GI. However, GI returned to normal by the 3rd postoperative day