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Exercise Capacity Deterioration in Patients With COPD^*

Longitudinal Evaluation Over 5 Years

^* From the Department of Respiratory Medicine (Drs. Oga, Sato, and Mishima), Graduate School of Medicine, Kyoto University, Kyoto; Respiratory Division (Dr. Nishimura), Kyoto-Katsura Hospital, Kyoto, Japan; Department of Respiratory Medicine (Dr. Tsukino), Hikone Municipal Hospital, Hikone, Japan; and Department of Cardiovascular and Respiratory Medicine (Dr. Hajiro), Shiga University of Medical Science, Otsu, Japan.

Correspondence to: Toru Oga, MD, Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, 53, Kawahara, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan; e-mail: ogat{at}df7.so-net.ne.jp

Background: Although exercise capacity is an important outcome measure in patients with COPD, its longitudinal course has not been analyzed in comparison to the change in pulmonary function.

Purpose: To examine how exercise capacity would deteriorate over time in patients with COPD, and what factors would contribute to it.

Methods: A total of 137 male outpatients with moderate-to-very-severe COPD were examined. The average age was 69.0 ± 6.6 years (± SD), and the mean postbronchodilator FEV₁ was 45.9 ± 15.4% predicted. Progressive cycle ergometry and pulmonary function testing were performed at entry, and every 6 months thereafter over 5 years. Due to the presence of missing data, a mixed-effect model analysis was then used to estimate the longitudinal changes in various clinical parameters.

Results: Peak oxygen uptake (O₂), peak minute ventilation (E), and peak tidal volume (VT) during exercise declined significantly over time (p < 0.0001), which was no less rapid than the deterioration in FEV₁. The mean decline rates for peak O₂ were 32 ± 60 mL/min/yr and 0.5 ± 1.0 mL/min/kg/yr. Multiple regression analysis revealed that the changes in peak E, peak VT, and peak respiratory rates were significant predictors for the change in peak O₂.

Conclusion: We demonstrated clear evidence of measurable and progressive deterioration in exercise capacity in COPD patients, which was no less rapid than the decline in airflow limitation. Dynamic ventilatory constraints during exercise also deteriorated over time, which most significantly contributed to this exercise capacity deterioration. In addition to pulmonary function, the longitudinal follow-up of exercise capacity is important not to miss the overall deterioration in COPD.

Key Words: airflow limitation • COPD • dynamic ventilatory constraint • exercise capacity • longitudinal study • progressive cycle ergometry

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