Individual profiles of dyspnoea and fatigue on chronic brochitic patients, defined by intensity and duration of submaximal workloads performed

The subjective perception of fatigue and dyspnoea during submaximal exercise was studied in 10 chronic bronchitic patients using Borg's CR10 scale, with the aim of developing a model for the assessment of sustainable workloads (through the definition of individual perceptual profiles). Each subject performed five trials, consisting of steptests at constant submaximal workloads. Fatigue (CRf) and dyspnoea (CRd) perceptions, heart rate (HR) and duration times were measured. Maximal duration was set at 30 min. The trial was stopped if a fatigue/dyspnoea score of 7 ("very strong") or 85% of the maximum HR was reached. The growth of fatigue and dyspnoea perceptions (R) as functions of time (S) were expressed by the formula: R = a + c (S-b)n. Parameters a, b, c and n calculated for each subject and trial were (mean and SD): a = 0.49 (0.31); b = 2 (0); c = 1.3 (0.61); and n = 0.55 (0.2) for dyspnoea; a = 0.51 (0.27); b = 2 (0); c = 1.4 (0.75); and n = 0.55 (0.2) for fatigue. Individual CR3 "iso-perception" curves (W = k t alpha) for fatigue and dyspnoea in a workload/duration reference system were computed from the experimental data obtained during the five trials. Mean values of the exponent alpha were (.0.5) +/- (-0.23) for dyspnoea, and (-0.41) +/- (-0.22) for fatigue. The CR3 "iso-perception" curves represented the subjectively acceptable level of exertion (defined for load and duration). By doubling the duration and workload, CRd score increments of 1.55 (SD 0.46) and 4.9 (SD 0.42), respectively, were computed. Subjective perceptions are correlated to the intensity and duration of submaximal workload performed, and can be used in conjunction with physiological parameters to predict acceptable workloads in chronic bronchitic patients.