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 FEV 1 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 FEV 1 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 FEV 1 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
FEV 1 and maximum oxygen uptake (VO2max), 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 FEV 1 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 FEV 1 do not predict changes in VO2max. We observed a correlation between the annual change in V Emax and annual change in VO2max (r = 0.51 p < 0.05). The baseline FEV 1 (expressed as a percentage of predicted and in absolute values) is the predictor of FEV 1 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.