Influence of ventilation inhomogeneity on diffusing capacity of carbon monoxide in smokers without COPD

Association of carbon monoxide diffusion capacity and ventilation inhomogeneity. Diffusing capacity of carbon monoxide (D_LCO) in % predicted is plotted versus a) lung clearance index (LCI) and b) S_acin normalised for tidal volume (V_T) as recommended (S_acin·V_T). Dashed lines display upper and lower limits of normal. Individuals are displayed as circles with a colour scale indicating smoking exposure (tertiles): open circles, 1–10 pack-years; light filled circles, 11–29 pack-years; dark filled circles, 30–60 pack-years.