NON-UNIFORM PULMONARY DIFFUSION AS DEMONSTRATED BY THE CARBON MONOXIDE EQUILIBRATION TECHNIQUE: EXPERIMENTAL RESULTS IN MAN *

Abstract

Data obtained during the simultaneous washout of carbon monoxide and helium from the lung indicate non-uniformity of diffusion throughout the lung. Using an assumed lung model to quantify this effect in five normal subjects, the lung behaves as though 6 to 18% of its volume contained 12 to 46% of its diffusing capacity (DL). In four of the normal subjects, total Dl from such calculations was not significantly different from that calculated by the breath holding technique. In five patients studied, variable degrees of non-uniformity of diffusion were noted. This phenomenon appeared to produce an unpredictible error in the breath holding method in abnormal subjects; in such subjects, it is believed that true DL cannot be accurately assessed by conventional techniques.