Effects of ascites and body position on gas exchange in patients with cirrhosis.

The effects of ascites and body position on gas exchange were evaluated in 22 male cirrhotics. All underwent spirometry and plethysmography in the sitting (erect) position. Single breath carbon monoxide diffusing capacity (DLco) was measured in the erect and supine positions in a random sequence. A significantly negative correlation was found between Kco (DLco corrected by alveolar volume [VA]) and lung volumes. DLco was significantly higher in the erect than in the supine position. On the other hand, Kco was significantly higher in the supine position. The differences of DLco and Kco between the erect and supine positions (the data in the supine minus those in the erect position) correlated highly with FEV1 and FVC. Thirteen patients underwent large volume paracentesis, and pulmonary function tests were done one day before and after paracentesis. Lung volumes and DLco increased significantly after paracentesis. In contrast, Kco decreased significantly. A significantly negative correlation was found between the change of Kco before and after paracentesis and that of lung volumes (the data after minus those before paracentesis). There was no remarkable change in the differences of DLco and Kco between the two positions after paracentesis. It is concluded that ascites may prevent further worsening of gas exchange and attenuate the postural effect on gas exchange in cirrhotic patients with significant amounts of ascites.