[Determinations of the carbon monoxide diffusion at the early stages of chronic obstructive lung disease]

The determinations of the diffusion capacity of lungs for carbon monoxide (DLco) with single breath or steady state methods find their elective indication in the diseases affecting electively the alevolar-capillar membrane, particularly in the cases of fibrosis. In the course of chronic obstructive bronchopneumopathies, they are more or less disturbed by the anomalies in the distribution of lung ventilation and perfusion that coexist with them in a constant mood. Nevertheless, it has been proved that the fall in DLco and in the relation DLco/alveolar volume is one of the elements that contribute to recognize lung emphysema and to make the distinction between the same and chronic bronchitis or asthma. It is also well established that DLco is lowered in the smokers, but the meaning of this fact is presently bad known: artefact due to the presence of carboxic-hemoglobin; lesion of the alveolar-capillar membrane or anomaly in the bronchiolar permeability. DLco is also diminished in some asymptomatic subjects bearers of a deficiency in alpha-l-antitrypsin and may be also encountered in the course of beginning lung emphysema with anatomic authentication. In some cases, the fall in DLco might therefore bear witness, prior to any spirographic alteration, of the involvement of the alveolar-capillar membrane, but not of the true bronchial obstruction.