Functional inhomogeneities in interstitial lung disease, assessed using (16)o(18)o

Abstract We investigated the contribution of diffusion limitation and functional inhomogeneities to the impairment of pulmonary oxygen (O(2)) transfer in interstitial lung disease (ILD). Analyses of (16)O(18)O/(16)O(2) ratios were performed on expiratory gas mixtures obtained from 6 ILD patients and 6 healthy humans at rest, applying respiratory mass spectrometry. We assessed O(2) transport by using the overall fractionation factor of respiration (α(0)) which is predicted to increase in the case of diffusion limitation. α(0) was reduced in patients (1.0065±3.10(-4)) when compared to the value for healthy subjects (1.0071±7.10(-4), P <0.05), pointing away from a diffusion limitation of O(2) transport. On the basis of a two-compartment model we interpreted our findings by assuming an unequal distribution of diffusion and convective O(2) transport in the pulmonary gas exchange of the patients.