Six years progression of exercise capacity in subjects with mild to moderate airflow obstruction, smoking and never smoking controls

Background Exercise capacity is an important feature in patients with COPD. Its impairment drives disability and dependency for daily activities performance. This study evaluated the six years change in exercise capacity in subjects with airflow obstruction and compared this to subjects without airflow obstruction, with and without a smoking history. Methods Cardiopulmonary exercise tests (CPET) were repeatedly performed during a six years follow up period. Peak oxygen uptake (VO2peak), work rate (WRpeak), heart rate (HRpeak), minute ventilation (VEpeak), respiratory exchange ratio (RERpeak) and ventilatory reserve (VE/MVV) were collected as effort dependent outcomes. The slopes of oxygen uptake, ventilatory and mechanical efficiency (OUES, ΔVE/ΔVCO2 and ΔVO2/ΔWR) were collected as effort independent outcomes. Results One hundred and thirty-eight subjects were included. Thirty-eight presented airflow obstruction (63±6 years, 74% men, FEV1 90±15%pred), 44 had a smoking history but no airflow obstruction (61±5 years, 61% men, FEV1 105±15%pred) and 56 had never smoked (61±7 years, 57% men, FEV1 117±18%pred). At baseline, the airflow obstruction group had slightly worse exercise capacity in comparison to the never smoking control group, in absolute terms and expressed as percentage of the predicted value (VO2peak = 27±5 versus 32±8 ml/min/kg, p<0.01; 112±29 versus 130±33%pred, p = 0.04). Most exercise variables showed a statistically significant yearly deterioration, with exception of VE/MVV, ΔVE/ΔVCO2 and ΔVO2/ΔWR. The yearly decline in VO2peak and OUES was not faster in subjects with airflow obstruction than in smoking and never smoking controls (VO2peak -67 (9) versus -76 (9) ml/min, p = 0.44 and versus -58 (9), p = 0.47; OUES -32 (11) versus -68 (10), p = 0.03 and versus -68 (13), p = 0.03). Conclusions With exception of VO2peak, effort dependent variables deteriorated faster in subjects with airflow obstruction compared to never smoking controls. The deterioration of effort independent variables, however, was not accelerated in the airflow obstruction group compared to controls.