Background: Diminished functional residual capacity and pulmonary collapse during general anesthesia lead to alterations in respiratory mechanics and gas exchange. Such phenomena are more pronounced in obese patients. We recently demonstrated the beneficial effects of the alveolar recruitment strategy on oxygenation in anesthetized patients of normal body mass index (BMI). The aim of the present study was to evaluate whether obese patients also benefit from the alveolar recruitment strategy and to determine the level of positive end-expiratory pressure (PEEP) that prevents recollapse in obese patients.
Methods: Three groups of 30 patients each were studied: patients with normal BMI (control group) and obese patients to whom we applied PEEP at 5 and 10 cm H2O (obese-5 and obese-10 groups, respectively) after the recruitment maneuver. We studied respiratory mechanics (respiratory distensibility, airway pressures and flow volume) and arterial oxygenation (PaO2) before and after the recruitment.
Results: PaO2 at baseline was higher in the control group (174 +/- 44 mm Hg) than in either the obese-5 or obese-10 group (108 +/- 24 and 114 +/- 22 mm Hg, respectively, p < 0.001). Oxygenation improved in all groups after recruitment (p < 0.001), and PaO2 in the obese-10 group was similar to that of the control group (218 +/- 25 mm Hg and 259 +/- 80 mm Hg, respectively, p > 0.05). Oxygenation in the obese-5 group, however, was worse (153 +/- 41 mm Hg) than that of either of the other groups (p < 0.001).
Conclusions: We conclude that the alveolar recruitment strategy was effective for increasing PaO2 in anesthetized patients, regardless of body mass. The oxygenation of obese patients receiving the higher level of PEEP was similar to that of non-obese patients.