Pre- and postoperative lung function in sitting and supine position related to postoperative chest X-ray abnormalities and arterial hypoxaemia.

Spirometry in both sitting and supine position was performed before and 3-5 days after elective upper abdominal surgery in 53 men, aged 41-72 years. The results were related to postoperative respiratory complications as defined by chest radiography and to measurements of the arterial oxygen tension. Preoperative total lung capacity (TLC), functional residual capacity (FRC) and wash-out volume (WOV) were lower in both positions among patients who were to develop major chest X-ray abnormalities than among patients with normal chest radiographs postoperatively. All patients who developed major chest X-ray abnormalities had a negative value for FRC - closing capacity (CC) in the supine position preoperatively, indicating 'airway closure' during tidal breathing. Preoperative WOV and lung clearance index (LCI) were higher in both sitting and supine positions in patients who developed postoperative hypoxaemia than in patients who did not. The postoperative decrease in TLC, FRC and WOV in the sitting position was greater among patients with major X-ray abnormalities and/or arterial hypoxemia postoperatively than among patients without these complications. According to our results, conventional spirometry in the supine position is not superior to conventional spirometry in the sitting position as part of pre- or post-operative assessment of patients. On the other hand, both preoperative 'airway closure' and arterial oxygen tension, measured in the supine position, showed a correlation with postoperative chest X-ray abnormalities.