Abnormal Exertional Breathlessness on Cardiopulmonary Cycle Exercise Testing in Relation to Self-Reported and Physiologic Responses in Chronic Airflow Limitation

Abstract

Exertional breathlessness is a cardinal symptom of cardiorespiratory disease. How does breathlessness abnormality, graded using normative reference equations during cardiopulmonary exercise testing (CPET), relate to self-reported and physiological responses in people with chronic airflow limitation (CAL)? An analysis was done of people aged≥ 40 years with CAL undergoing CPET in the Canadian Cohort Obstructive Lung Disease study. Breathlessness intensity ratings (Borg CR10 scale [0-10 category-ratio scale for breathlessness intensity rating]) were evaluated in relation to power output (W), rate of oxygen uptake (V˙o2), and minute ventilation (V˙e) at peak exercise, using normative reference equations as follows: (1) probability of breathlessness normality (probability of having an equal or greater Borg CR10 rating among healthy; lower probability reflecting more severe breathlessness) and (2) presence of abnormal breathlessness (rating above the upper limit of normal). Associations with relevant participant-reported and physiologic outcomes were evaluated. We included 330 participants (44%women): mean ± SD age, 64 ± 10 years (range, 40-89 years); FEV1/FVC, 57.3%± 8.2%; FEV1, 75.6%± 17.9%predicted. Abnormally low exercise capacity (peak V˙o2< lower limit of normal) was present in 26%. Relative to peak W, V˙o2, and V˙e, abnormally high breathlessness was present in 26%, 25%, and 18%of participants. For all equations, abnormally high exertional breathlessness was associated with worse lung function, exercise capacity, self-reported symptom burden, physical activity, and health-related quality of life; and greater physiological abnormalities during CPET. Abnormal breathlessness graded using CPET normative reference equations was associated with worse clinical, physiological, and functional outcomes in people with CAL, supporting construct validity of abnormal exertional breathlessness.