Abstracts Biological Sciences

Surface tension and distribution of ventilation within the lung

by Mary Rona

The pressure-volume characteristics and the regional distribution of liquid ventilation in left lower lobes of excised dogs' lungs were determined by infusion of saline containing I131 labelled albumin into preparations suspended in a second liquid, whose density was lower than that of the ventilating liquid. Surface tension in the lung was thereby abolished, and a vertical transpulmonary pressure gradient was created. The elastic properties of the lung were therefore altered and the pressure-volume curve was no longer exponential as it is during ventilation with air. Above functional residual capacity ventilation was distributed preferentially to the alveoli of the upper zones. The pattern of filling was sequential: namely, the proportion of a tidal breath reaching a given alveolus was not constant but varied with preinspiratory volume. It was shown that this altered pattern of ventilation could be explained by the changes in the elastic properties of the liquid-filled lung.