[THE CELLULAR MECHANISMS OF LUNG EDEMA CLEARANCE: DOES THE ALVEOLAR EPITHELIUM PLAY A ROLE?].

Pulmonary edema develops as a result of either alteration in the hydrostatic and oncotic pressure gradients across the pulmonary circulation and the lung interstitium or due to increased lung permeability. Alveolar fluid clearance is important in keeping the airspaces free of edema. This process is carried out via the alveolar epithelial active transport of Na+ across the alveolo-capillary barrier mostly by apical Na+ channels and basolateral Na,K-ATPases. Several pharmacologic agents such as catecholamines, vasopressin and gene therapy interventions have currently been found to stimulate the active Na+ transport and lung edema clearance. While others such as amiloride, ouabain, high tidal volume ventilation, hyperoxia and sepsis decrease the rate of alveolar fluid clearance. In conclusion, this review discusses the mechanisms and signal pathways by which the alveolar epithelium impacts lung edema clearance.