Critical Role of the Alveolar Epithelial Barrier

Abstract

The overall objective of this chapter is to consider the role of the alveolar epithelial barrier in the development and the resolution of acute lung injury. The chapter is divided into five sections. The first examines the role of the alveolar epithelial barrier in maintaining lung fluid balance in the uninjured lung, with an emphasis on the role of sodium transport and the recently discovered water channels for regulating fluid transport across the alveolar epithelial barrier. The second section focuses on the central role of the alveolar epithelial barrier in acute lung injury and includes a discussion of the concept that the degree of alveolar barrier disruption is a major determinant of the severity of experimental and clinical acute lung injury. The third section discusses the function of the alveolar barrier in acute lung injury, emphasizing that the degree of damage ranges from mild to severe. This section also briefly reviews some of the mechanisms that may be important in causing injury to the alveolar epithelial barrier. The fourth section reviews data on the effects of endogenous and exogenous catecholamines on the function of the alveolar epithelial barrier under pathological conditions, a topic with several important clinical implications. The final section considers new strategies for attenuating or preventing lung endothelial and epithelial injury in adult patients with the syndrome of acute respiratory distress (ARDS).