Modification of Sodium Transport and Alveolar Fluid Clearance by Hypoxia

Karin M. Hardiman and Sadis Matalon

Departments of Physiology and Biophysics and Anesthesiology, Schools of Medicine and Dentistry, University of Alabama at Birmingham, Birmingham, Alabama

In order for gas exchange to occur optimally, the alveoli must remain open and free from fluid. In utero, the fetal lung is filled with fluid which is removed shortly after birth, mainlybecause active reabsorption of sodium ions (Na+) across the alveolar epithelium creates an osmotic force favoring reabsorption of alveolar fluid (1, 2)

There have been numerous studies attempting to identify whether decreased alveolar fluid clearance (AFC) contributes to alveolaredema formation in a variety of pathophysiologic conditions. The results of several studies suggest that severe alveolar hypoxia results in decreased AFC and Na+ transport (see Table 1). This is of major interest because alveolar hypoxemia may be encountered in a variety of pathologic conditions including hypoventilation, obstructive lung disease, and ascent to high altitude (15).