Is Lung Weight an Important Determinant of the Topographic Distribution of Regional Volume?
Research on normal animals conducted in the 1970s and 1980s established that lung weight accounts for no more than 20% of the vertical gradient in pleural pressure and alveolar volume (33 37). In other words, under normal conditions lung weight is only a minor determinant of the topographic distribution of parenchymal stress and strain. This can be appreciated intuitively by noting that gravitational gradients in pressure and volume vary considerably with posture (even though lung weight is more or less the same in all postures). Before considering whether lung weight plays a greater role in injury states, it might be helpful to review some fundamental continuum mechanics concepts (37, 38). To an engineer, the in situ distribution of lung parenchymal pressure and volume is a shape-matching problem between two gravitationally deformed elastic solids: the lungs and the chest wall (including heart and mediastinum). The cartoon in Figure 1 shows a very simple, but nevertheless instructive,
