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'/V'CO). Thus, smokers with reduced lung carbon monoxide diffusion capacity (D) have a heightened V'/V'CO 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 were compared to 15 smokers with normal D. Accuracy through sensibility and specificity for V'/V'CO slope and nadir was compared with a new index for ventilatory efficiency (ηV',%), to uncover early diffusive changes in smokers without COPD.