Lung mechanics during upper abdominal surgery.

Functional residual capacity (FRC) and breath-by-breath compliance of the respiratory system (Crs) were studied after induction of anaesthesia, after insertion of retractors and after wound closure in patients undergoing upper abdominal surgery via a subcostal (n = 8) or a midline (n = 8) incision. After anaesthesia induction the mean FRC was 1.6 +/- 0.3 l. In the subcostal incision group FRC did not change between the studied stages, but Crs fell after retractor placement from 51 +/- 3 to 43 +/- 5 ml/cmH2O (p less than 0.01). In the midline incision group FRC rose by 21% (p less than 0.01) when the retractors were inserted, but regained outset level after wound closure. Crs in this group did not change significantly after retraction, but after closure of the wound it fell to 44 +/- 6 ml/cmH2O, i.e. less (p less than 0.05) than the outset value (52.6 ml/cmH2O). FRC thus did not decrease in either group, but Crs fell by about 15%. The authors conclude that the known difference in postoperative pulmonary complications between midline vs. subcostal incisions is not caused by the studied intraoperative events.