A new ventilatory efficiency index and accuracy for early lung diffusion impairment in non-COPD smokers

In smokers without manifest airway obstruction, early emphysema and endothelial dysfunction has been related to minute-ventilation/carbon dioxide output ratio (V'_E/V'CO₂). Thus, smokers with reduced lung carbon monoxide diffusion capacity (D_Lco) have a heightened V'_E/V'CO₂ ratio. We hypothesized that ventilatory inefficiency could contribute to the suspicion of impaired diffusive capacity in the absence of significant airway obstruction. Thus, 15 smokers with impaired D_Lco were compared to 15 smokers with normal D_Lco. Accuracy through sensibility and specificity for V'_E/V'CO₂ slope and nadir was compared with a new index for ventilatory efficiency (ηV'_E,%), to uncover early diffusive changes in smokers without COPD.