Severe hypoxemia and liver disease.

Severe hypoxemia and orthodeoxia in patients with chronic liver disease is uncommon, but, when present, it is incapacitating. The purpose of this study was to determine the distribution of alveolar ventilation-perfusion (VA/Q) in six patients with mild liver disease and severe hypoxemia (PaO2 at rest in sitting or standing position ranged from 35 to 67 mm Hg). Orthodeoxia was documented with improvement in PaO2 in the supine position in each patient (PaO2 at rest in supine position ranged from 46 to 75 mm Hg). VA/Q distribution was measured by the multiple inert gas elimination technique. The dispersion of VA/Q was increased with small portions of the cardiac output (0.5 to 14.8%) perfusing low VA/Q areas (O less than VA/Q less than 0.1). Another major finding was a large right-to-left shunt (VA/Q less than 0.005) that ranged from 4 to 28%. The VA/Q mismatching and the right-to-left shunt both contributed to the hypoxemia. The predicted PaO2 was 5.5 mm Hg (p less than 0.01) larger than the measured PaO2. In each patient, the mean pulmonary artery pressure was low and the cardiac output was elevated. These results show that the low PaO2 in these patients was due to both increased right-to-left shunt and VA/Q mismatching, but impaired diffusion could not be ruled out.