EFFECT OF INCREASED STATIC LUNG RECOIL ON VENTILATION DISTRIBUTION IN EXCISED HUMAN LUNGS

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Abstract
The contour of a modified Fowler single-breath N2 washout was determined in 15 postmortem human lungs before and after static lung recoil was increased by ventilation. Before ventilation, expiratory N2 vs. volume curves exhibited the 4 phases similar to those seen in intact human lungs. The tests were repeated after ventilation with humidified air at room temperature for 3 h at pleural pressures between -20 and +10 cm H2 at 15 breaths/min. After ventilation, the slope of the alveolar plateau (Phase III) decreased (P < 0.01); the volume of Phase IV increased (P < 0.01) and the closing capacity (Phase IV plus minimal volume) decreased (P < 0.01). In the human lung, the onset of Phase IV is apparently not solely dependent on a pleural pressure gradient and that after ventilation, when static lung recoil is increased, the distribution of inspired gas in the excised human lung is more uniform, and at least some lung units empty more completely before zero transpulmonary pressure is reached.