Mechanical Forces Impair Alveolar Ion Transport Processes – A Putative Mechanism Contributing to the Formation of Pulmonary Edema

The aim of this chapter is to highlight the importance of transepithelial ion transport processes for lung function in general and to focus on the impact of mechanical forces on pulmonary ion transport in particular. Linking mechanical forces with pulmonary ion transport derives from the fact that the lung is a dynamic organ as well as from several studies providing evidence that the amount of mechanical forces as used during artificial ventilation correlates with mortality rates in patients with respiratory failure such as ALI (acute lung injury) and ARDS (acute respiratory distress syndrome) (ARDS Network Investigators, 2000). In these patients the formation of pulmonary edema is a characteristic symptom (Frank and Matthay, 2003; Ricard et al., 2003) and the basic rationale behind this is, that mechanical perturbations cause epithelial leakage in response to mechanically induced damage of the epithelial layer. This damage is suggested to be a major cause for the formation of pulmonary edema as well as the inability to reabsorb the edema fluid. However, little is known whether or not mechanical forces may directly interfere with pulmonary ion transport processes and this represents a putative mechanism that facilitates the formation of pulmonary edema – in addition to damages of the epithelial layer.