@article {ElbehairyP2106, author = {Amany Elbehairy and Azmy Faisal and Casey Ciavaglia and Daniel Langer and Megan Preston and Katherine Webb and J. Alberto Neder and Denis O{\textquoteright}Donnell}, title = {Is ventilatory efficiency impaired during progressive exercise in mild COPD?}, volume = {44}, number = {Suppl 58}, elocation-id = {P2106}, year = {2014}, publisher = {European Respiratory Society}, abstract = {Abnormalities in ventilation-perfusion matching may start early in the natural history of COPD. These disturbances are likely to worsen under increased ventilatory demands {\textendash} as those elicited by exercise. Therefore, measurements of exercise ventilatory efficiency (ventilation (V{\textquoteright}E) to carbon dioxide output (V{\textquoteright}CO2)) could be valuable to uncover those abnormalities in mild COPD. Forty GOLD grade I patients and 20 controls underwent an incremental cardiopulmonary exercise test. The V{\textquoteright}E-to-V{\textquoteright}CO2 relationship was expressed as slope and intercept or as a ratio (V{\textquoteright}E/V{\textquoteright}CO2) at its lowest point (nadir). Peak exercise capacity and sub-maximal O2 saturation were lower in patients (p\<0.05). Despite the lack of differences in V{\textquoteright}E-V{\textquoteright}CO2 slope, V{\textquoteright}E/V{\textquoteright}CO2 nadir was higher in patients. This was consequence of greater intercepts (Table); in fact, nadir-slope differences were associated with larger intercepts (r= 0.60; p\<0.01). In line with these data, end-tidal expiratory pressure for CO2 (PETCO2) was reduced throughout exercise. Patients with higher nadirs (\> median) had lower lung diffusing capacity (p= 0.05) and peak oxygen uptake (p\<0.05).Excessive ventilatory responses to metabolic demand and impaired oxygenation in GOLD grade I patients indicates that the efficiency of the lung as gas exchanger is compromised despite a preserved FEV1. The impact of treatment strategies on these outcomes deserves further consideration in this patient sub-population.}, issn = {0903-1936}, URL = {https://erj.ersjournals.com/content/44/Suppl_58/P2106}, eprint = {https://erj.ersjournals.com/content}, journal = {European Respiratory Journal} }