Mechanisms of gas exchange impairment in patients with liver cirrhosis

The term hepatopulmonary syndrome refers to the abnormal pulmonary gas exchange that often occurs in patients with cirrhosis in the apparent absence of any intrinsic heart or lung disease. This article reviews the pathophysiologic mechanisms underlying this syndrome. The effects of hypoxia, hyperoxia, and exercise on the degree of ventilation-perfusion inequality and intrapulmonary shunt, and the diffusion of oxygen from the alveoli to the capillary blood are considered. Potential pathogenic pathways are outlined. Finally, the effects of external interventions on pulmonary gas exchange are evaluated. These studies suggest that an abnormal regulation of pulmonary vascular tone is the main cause of the defective pulmonary gas exchange seen in patients with hepatopulmonary syndrome.