Biomechanical modeling of an alveolar sac for simulation of septal stresses in pulmonary edema

Experimental studies have shown that high pulmonary pressures occurring during ventilation may damage the capillary walls and lead to pulmonary edema. Knowledge of the structural stress distribution within the alveolar septa is a basic first step towards understanding this phenomenon. A two-dimensional alveolar sac model was developed for analysis of stress distribution in septal walls of a saline-filled lung. A parenchymal micrograph was digitized to yield a geometric replica of a typical alveolar sac. Stress concentrations were shown to develop near curved regions, where both tension and compression values may be as high as 20 times that of average stresses. These stresses and the cyclic loading of mechanical ventilation may increase the gaps between the endothelial cells of the capillary walls, and thereby, give rise to pulmonary edema