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 (V̇A/Q̇) in six patients with mild liver disease and severe hypoxemia (Pa(O₂) at rest in sitting or standing position ranged from 35 to 67 mm Hg). Orthodeoxia was documented with improvement in Pa(O₂) in the supine position in each patient (Pa(O₂) at rest in supine position ranged from 46 to 75 mm Hg). V̇A/Q̇ distribution was measured by the multiple inert gas elimination technique. The dispersion of V̇A/Q̇ was increased with small portions of the cardiac output (0.5 to 14.8%) perfusing low V̇A/Q̇ areas (O < V̇A/Q̇ < 0.1). Another major finding was a large right-to-left shunt (Ȧ/Q̇ < 0.005) that ranged from 4 to 28%. The V̇A/Q̇ mismatching and the right-to-left shunt both contributed to the hypoxemia. The predicted Pa(O2) was 5.5 mm Hg (p < 0.01) larger than the measured Pa(O₂). In each patient, the mean pulmonary artery pressure was low and the cardiac output was elevated. These results show that the low Pa(O₂) in these patients was due to both increased right-to-left shunt and V̇A/Q̇ mismatching, but impaired diffusion could not be ruled out.