Rate of lung collapse after airway occlusion on 100% O₂ at various ambient pressures

¹ Department of Physiology, State University of New York at Buffalo, Buffalo, New York

The volume, time, and rate of collapse of the lungs following tracheal occlusion were studied in rats breathing O₂ at ambient pressures between 1,520 mm (2 atm) and 190 mm (equivalent to 33,000 ft altitude). Theoretical calculations and experimental data show that 1) the rate of lung collapse is directly related to the O₂ uptake and inversely related to the barometric pressure minus the sum of alveolar CO₂ and water vapor pressure, and 2) the total time required for producing complete lung collapse is proportional to the lung volume at the time of occlusion and to the barometric pressure minus the sum of alveolar CO₂ and water vapor pressure and inversely proportional to the O₂ uptake. In both these relationships, lung volume is expressed at BTPS, while the O₂ uptake is at STPD. The collapse time, with the lungs occluded at functional residual capacity dropped from 22.6 sec at sea level to 3.5 sec at 190 mm Hg. The rate of collapse was found to remain essentially constant during any experiment, as could be predicted from the analysis of the factors involved. The time required for collapse, in any species, at any lung volume and Vo₂, can be determined with a nomogram.

Submitted on July 7, 1964