Study objective: Low-grade systemic inflammation may cause a chronic catabolic state that may affect trainability in patients with COPD as has been seen previously in healthy elderly. Therefore, the aim of the present study was to study the relationship between baseline circulating levels of inflammatory markers and the response to exercise training in clinically stable patients with COPD.
Design: An open prospective intervention study.
Setting: Tertiary care setting, University Hospital Gasthuisberg, Leuven, Belgium.
Patients: Seventy-eight clinically stable outpatients with COPD.
Intervention: A 12-week outpatient exercise-training program consisting of strengthening and endurance types of exercises.
Measurements and results: Circulating levels of inflammatory markers were assessed at baseline. Moreover, lung function, quadriceps force (QF), peak and functional exercise capacity, and health-related quality of life were determined at baseline and after the intervention. Sixty-five of the 78 consecutive outpatients completed the study protocol. QF, peak and functional exercise capacity and health-related quality of life improved significantly compared to baseline. The absolute changes in health-related quality of life showed weak relationships with baseline circulating levels of interleukin-8 (CXCL8) in the whole group (n = 65; r= −0.26; p = 0.04). In addition, soluble tumor necrosis factor receptor p55 was strongly and positively related to the absolute changes in QF in the female patients only (n = 18; r = 0.81; p = 0.0001), while CXCL8 was inversely related to the absolute change in the total score of the Chronic Respiratory Disease Questionnaire (r= −0.65; p = 0.004).
Conclusion: Baseline markers of low-grade systemic inflammation did not clearly explain the variances in absolute changes in QF, the distance walked in 6 min, peak external load, or health-related quality of life following a 12-week exercise-training program. Hence, they seem not very constructive in the characterization of patients with advanced COPD who do or do not respond to exercise training.