REPRODUCIBILITY OF BORG SCALE MEASUREMENTS OF DYSPNEA DURING EXERCISEIN PATIENTS WITH COPD

The purpose of this study was to evaluate the moderate term (5 weeks) reproducibility of Borg scale ratings of the effort to breathe (Borg(e )) and the degree of discomfort evoked by breathing (Borg(d)) in patie nts with COPD during exercise. Six subjects with moderately severe COP D (FEV(1), 1.42+/-0.50 L) underwent progressive incremental exercise ( 15 W/min) on a cycle ergometer to a symptom-limited maximum every week for 6 weeks (first week used as practice session). Minute ventilation (VE), oxygen consumption (VO2), and Borg ratings were obtained every minute during exercise. Borg(e) and Borg(d) were highly correlated in each subject (r=0.99+/-0.01). Borg scores were not significantly diffe rent across study days during both maximal and submaximal exercise. Th e within-subject coefficient of variation (CV) for Borg(e) during maxi mal exercise was 13.9+/-9.0% (range, 6 to 31%) which was not significa ntly different from that observed for the physiological indices: 8.2+/ -4.1% (range, 4 to 15%) for VE and 5.2+/-3.4% (range, 1 to 10%) for VO 2. In contrast, at 66% of the maximum workload, the within-subject CV for Borg(e) was 25.0+/-13.6% (range, 12 to 50%) which was significantl y greater than that observed for the physiologic indices: 5.8+/-2.0% ( range, 3 to 9%) for VE and 4.6+/-1.1% (range, 3 to 6%) for VO2. In eve ry subject, Borg(e) was linearly correlated with VE, VO2, and workload . However, within an individual subject, the slope of these relationsh ips varied between trials; within-subject CV for the slope of the Borg (e)/VE relationship was 20.2+/-8.0% (range, 12 to 32%). In conclusion, during incremental exercise Borg ratings of dyspnea are not as reprod ucible as physiologic indices in patients with COPD.