When to Best Assess Breathlessness Abnormality During Incremental Cardiopulmonary Cycle Exercise Testing.

Abstract

Breathlessness on exertion is a common, distressing, and limiting symptom that can be quantified on incremental cardiopulmonary exercise testing (CPET) using normative reference equations. Is the breathlessness abnormality best uncovered and assessed at symptom limitation (peak exercise) compared with submaximal exercise intensities? This was an analysis of people ≥ 40 years of age undergoing symptom-limited incremental cycle CPET in the Canadian Cohort Obstructive Lung Disease (CanCOLD) study. Each Borg 0-10 category ratio scale breathlessness intensity rating during CPET was converted to its probability of being normal, in relation to power output, rate of oxygen uptake, and minute ventilation using normative reference equations. Abnormally high exertional breathlessness (abnormal breathlessness) was defined as a probability of being normal < 0.05. Of 1,161 participants (42% female), abnormally high breathlessness was present in 22%, 23%, and 16% in relation to rate of oxygen uptake and minute ventilation at peak exercise. Among those with abnormal breathlessness at peak exercise, 55% to 60% had normal breathlessness across all submaximal exercise intensities. Among those with normal breathlessness at peak exercise, 93% to 97% were normal across all serial breathlessness ratings throughout the CPET (interclass correlation coefficients, 0.93-0.95). Findings were similar in people with or without chronic airflow limitation, and in people who did or did not reach maximal exertion at the end (symptom limitation) of the CPET. The results of this study suggest that abnormal breathlessness is uncovered and should be assessed at peak exercise during symptom-limited incremental CPET. These findings inform symptom assessment in research and clinical practice.