Evaluation of COPD Progression Based on Spirometry and Exercise Capacity

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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. 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. 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). 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.