Exercise Tolerance According to the Definition of Airflow Obstruction in Smokers

Neder et al discuss their study on exercise tolerance according to the definition of airflow obstruction in smokers. The clinical significance of an FEV/FVC ratio between 0.7 and the lower limit of normal in previous and current smokers remains highly controversial. The key issue is whether subjects in the so-called gray zone have an increased probability of airflow obstruction, a central construct for the diagnosis of chronic obstructive pulmonary disease (COPD). Apart from statistical considerations, a common approach involves a comparison of subjects with a "discordant" ratio against subjects with "concordant (positive)" (obstruction by both criteria) and "concordant (negative)" ratios (no obstruction by both criteria) vis-a-vis structural abnormalities (emphysema burden or airway disease) and negative health outcomes such as respiratory hospitalizations.