Pulmonary diffusing capacities for oxygen-labeled CO2 and nitric oxide in rabbits

Abstract

Heller, Hartmut, Gabi Fuchs, and Klaus-Dieter Schuster. Pulmonary diffusing capacities for oxygen-labeled CO2 and nitric oxide in rabbits. J. Appl. Physiol. 84(2): 606–611, 1998.—We determined the pulmonary diffusing capacity (Dl) for18O-labeled CO2(C18O2) and nitric oxide (NO) to estimate the membrane component of the respective gas conductances. Six anesthetized paralyzed rabbits were ventilated by a computerized ventilatory servo system. Single-breath maneuvers were automatically performed by inflating the lungs with gas mixtures containing 0.9% C18O2or 0.05% NO in nitrogen, with breath-holding periods ranging from 0 to 1 s for C18O2and from 2 to 8 s for NO. The alveolar partial pressures of C18O2and NO were determined by using respiratory mass spectrometry. Dl was calculated from gas exchange during inflation, breath hold, and deflation. We obtained values of 14.0 ± 1.1 and 2.2 ± 0.1 (mean value ± SD) ml ⋅ mmHg−1 ⋅ min−1for[Formula: see text]and Dl NO, respectively. The measured[Formula: see text]/Dl NOratio was one-half that of the theoretically predicted value according to Graham’s law (6.3 ± 0.5 vs. 12, respectively). Analyses of the several mechanisms influencing the determination of[Formula: see text]and Dl NOand their ratio are discussed. An underestimation of the membrane diffusing component for CO2 is considered the likely reason for the low[Formula: see text]/Dl NOratio obtained.