Measurement of Lung Volume by Rapid Decompression

Abstract

A study of some of the factors involved in measuring lung volume by the volume expansion method has revealed that the diffusion of gas into the air passages under certain conditions may be the source of considerable error. An attempt was made to correct this error. The effusion of gas out of the lungs at low pressure was directly measured and found to increase greatly at pressures below 150 mm Hg. At these pressures the uptake of O2 is impaired or reversed while the liberation of CO2 may be temporarily increased. Using the corrections devised it was found that the functional residual capacity of nembutalized supine dogs was 30.7 [plus or minus] 2.6 ml/kg body weight at rectal temperatures between 36 and 38.5[degree]C. Hyperthermia was found to increase the rate of effusion at pressures which produce severe hypoxia.