Background: The American Thoracic Society (ATS)/European Respiratory Society (ERS)-Global Initiative for Chronic Obstructive Lung Disease (GOLD) has developed a new staging system based on the degree of airflow obstruction. Its validity to predict exercise capacity as an outcome has not been extensively studied. We hypothesized that exercise performance measured by cardiopulmonary exercise test (CPET) results should decline significantly with each disease stage, independent of gender.
Methods: We examined 453 consecutive incremental CPET and pulmonary function tests performed in patients who had been referred to a single respiratory physiology laboratory in a tertiary care hospital. They were divided into a control group (normal lung function) and ATS/ERS-GOLD stages 1 to 4. We measured anthropometrics, peak work (in watts), peak oxygen uptake (in liters per kilogram per minute and percent predicted), breathing reserve (in percent predicted), and arterial blood gas response. We compared these results between different stages and genders.
Results: The mean (+/- SD) age for the entire group was 64 +/- 11 years, the mean FEV(1) was 66 +/- 28%, and the mean body mass index (BMI) was 27.2 +/- 5.82 kg/m(2). Patients in stage 4 were significantly younger (p < 0.001) and had a lower BMI (p < 0.02) compared to those in stages 1 to 3. There was a significant reduction in exercise capacity for patients at every stage except for those in stage 1, who had values similar to those of the control group. Women had better lung function and exercise capacity than men, but the difference disappeared when adjusted by COPD stages.
Conclusions: The ATS/ERS-GOLD staging system can be used to indicate differences in exercise capacity in patients with COPD stages 2 to 4 and to normalize apparent gender disparities. The value of differentiating stage 1 patients requires further studies with different outcomes.