Dyspnea ratings for prescribing exercise intensity in patients with COPD

Study objective: We tested the hypothesis that patients with COPD can use dyspnea ratings obtained from a prior graded exercise test as a target to reliably produce specific exercise intensities. Design: Four visits over a 7-week period. Setting: Pulmonary function and cardiorespiratory exercise laboratory at a university hospital. Patients: Fifteen symptomatic patients with stable COPD, Age was 68+/-7 (mean+/-SD) years, FEV(1) was 1.12+/-0.22 L (45+/-8% predicted). Interventions: At each visit, patients estimated the heaviness of weights to evaluate their magnitude estimation of a nonrespiratory task; after pulmonary function testing was completed, patients were tested on the cycle ergometer, At estimation trial 1 (day 0), patients estimated the intensity of dyspnea using the 0 to 10 category-ratio scale during an incremental exercise test. Estimation trial 2 (day 5 to 7) was the same as the previous trial, At production trials 1 (day 10 to 14) and 2 (day 40 to 44), patients were instructed to produce specific intensities of dyspnea tie, dyspnea targets) at 50% and at anaerobic threshold (AT) or 80% of peak oxygen consumption (Vo(2)) as calculated from results at estimation trial 2. Measurements and results: Lung function was stable at all visits, Dyspnea ratings were 1.8+/-0.9 (range, 1 to 3) at 50% of peak Vo(2) and 5.5+/-1.5 (range, 4 to 8) at AT/80% of peak Vo(2) (17.0+/-3.4 mL/kg/min) at estimation trial 2. The individual percent changes in Vo(2) at the lower dyspnea target were 12+/-19% and 11+/-19% for production trials 1 and 2, respectively, compared with estimation trial 2. At the higher dyspnea target, the corresponding individual percent changes in Vo(2) were -4+/-9% and -7+/-11%, respectively. For all 15 patients, there were borderline statistical differences for the Vo(2) values at the lower (p=0.04 and p=0.07) and at the higher (p=0.04 for each production Mall dyspnea targets for production trials 1 and 2 compared with estimation trial 2. Two patients showed 50% or greater variability in the calculated exponent for magnitude estimation of weights, In a subgroup analysis of the 13 patients with reproducible magnitude estimation of the heaviness of weights, there were no significant differences in Vo(2) for the two production trials compared with estimation trial 2 at both exercise intensities. Conclusions: Dyspnea ratings obtained from an incremental exercise test can be used as a target for patients with COPD to regulate/monitor the intensity of exercise training. The ability of patients with COPD to achieve a desired Vo(2) based on an individual dyspnea target was generally more accurate at the higher exercise level (AT/80% of peak Vo(2)) compared with the lower intensity (50% of peak Vo(2)). Acceptable accuracy was maintained over a 5-week time period.