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expansion of different regions of the lungs at various lung volumes was measured in nine seated normal men, using xel? * Regional volumes (expressed as a fraction of the volume of each region at maximal inspiration) were always greater in upper than in lower lung zones. When lung volume was increased from residual volume to about 207 ~ vital ca-pacity, the changes in regional lung volume (expressed as a fraction of the volume of each region at maximal inspiration) were greater in upper than in lower lung regions, whereas the opposite was true at higher lung volumes. From these data it was possible to describe systematically the effect on regional distribution of ventilation of varying both preinspiratory lung volume and tidal volume. Evidence is presented suggesting that the uneven distribution of ventilation in the normal lung is the consequence of regional differences in pleural pressure.
Milic‐Emili et al. (Sun,) studied this question.