Evaluation of COPD Progression Based on Spirometry and Exercise Capacity

Introduction: Chronic obstructive pulmonary disease (COPD) is characterized by an airflow limitation that is usually progressive. The progression of COPD expressed as the rate of an annual decline in FEV₁ is very heterogeneous. Exercise capacity in COPD patients is often diminished and becomes worsened over the time. The purpose of the study was to examine how the change in FEV₁ and exercise capacity would deteriorate over long-term observation. Material and Methods: A total of 22 men with COPD were examined. At the beginning the average age was 59 ± 8.1 years and the mean post-bronchodilator FEV₁ was 52 ± 14.9% predicted. Pulmonary function testing was performed at entry and then each year for 10 years, and exercise testing on a cycle ergometer was performed at entry and after 10 years. Results: FEV₁ and maximum oxygen uptake (VO_2max), maximum mechanical work (W_max), maximum minute ventilation (V_Emax) and maximum tidal volume (V_Tmax) declined significantly over the observation time. The mean annual decline in FEV₁ was 42 ± 37 mL, and the mean decline for VO 2max was 30 ± 15 mL/min/yr and 0.44 ± 0.25 mL/min/kg/yr. Regression analysis revealed that the changes in FEV₁ do not predict changes in VO_2max. We observed a correlation between the annual change in V_Emax and annual change in VO_2max (r = 0.51; p < 0.05). The baseline FEV₁ (expressed as a percentage of predicted and in absolute values) is the predictor of FEV₁ annual decline (r = 0.74 and 0.82; p < 0.05). Conclusions: We observed over time deterioration in exercise capacity in COPD patients which is independent of decline in airflow limitation. The long term follow-up of exercise capacity is important in monitoring of COPD patients in addition to pulmonary function.