Changes in exhaled pulmonary diffusing capacity at rest and exercise in individuals with impaired positional diffusion
McClean, P.A.; Duguid, N.J.; Griffin, P.M.; Newth, C.J.; Zamel, N.
Bulletin Europeen de Physiopathologie Respiratoire 17(2): 179-186
1981
ISSN/ISBN: 0395-3890 PMID: 7284645 Document Number: 174128
To investigate the mechanism of impairment in increasing CO diffusion between sitting and supine postures (.DELTA.KCO) which was found predominantly in smokers, the exhaled CO lung diffusing capacity, DLCOE, was measured at different lung volumes during the course of a single exhalation at rest and immediately following exercise in 6 individuals with normal .DELTA.KCO (reactors) and in 6 individuals with low .DELTA.KCO (nonreactors). DLCOE was calculated for every 10% of vital capacity (VC) by continuously measuring C12O18 and Ar in the expirate during slow exhalation. DLCOE increased significantly (P < 0.05) in the last 20% VC during exercise in the reactors, but not in the nonreactors. Since the last portion of VC during a slow exhalation is expired predominantly from the apices, it can be speculated that the increase of DLCOE during exercise at these lung volumes reflects the ability of the apices to recruit pulmonary blood volume. The mechanism of the inability of DLCOE to increase in the nonreactors durin exercise is still obscure; it may be related to abnormal apical vascularity which could be due to early emphysema.