[The value of studies of pulmonary gas exchange during exercise for evaluation of reduced arterial oxygenation at rest in asymptomatic long-term smokers].

The aim of this study was to elucidate extent and nature of an impairment of gas exchange after long time cigarette-smoking. Pulmonary gas exchange at rest as well as during steady state exercise and conventional lung function tests (LFTs) were studied in 32 clinically healthy, asymptomatic severe cigarette-smokers (S; 48.1 +/- 15.7 pack-years) and 32 healthy lifetime nonsmokers (N) between 40 and 60 years of age, respectively, individually matched for age, body height, body weight and gender. Pulmonary function tests of all subjects were within the limits of normal values. Except for a slight reduction of MEF25 in S (p < 0.05) and a slight increase of FRC (p < 0.05), the groups did not differ with respect to LFTs. At rest, however, S had markedly lower values for PaO2, TLO2, DCO and KCO, and higher values for AaDO2 and QVA/Qt. Resting measurements for VD/VE and PaCO2 did not differ between N and S. During ergometry PaO2 and TLO2 increased respectively; AaDO2 and QVA/Qt fell concomitantly with VD/VE and PaCO2. On termination of exercise no significant difference between N and S for the above variables could be discerned any longer. Our findings confirm that even in clinically healthy asymptomatic cigarette-smokers a distinct impairment of gas exchange is present. Their improvement during physical exercise primarily indicates the presence of reversible ventilation-perfusion mismatching and excludes relevant morphologic changes in the lung in these cases.