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

Background: Exertional breathlessness is a cardinal symptom of cardiorespiratory disease.

Research Question: How does breathlessness abnormality, graded using normative reference equations during cardiopulmonary exercise testing (CPET), relate to self-reported and physiologic responses in people with chronic airflow limitation (CAL)?

Study Design And Methods: 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, rate of oxygen uptake, and minute ventilation 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 people; 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.

Results: We included 330 participants (44% women): mean ± SD age, 64 ± 10 years (range, 40-89 years); FEV/FVC, 57.3% ± 8.2%; FEV, 75.6% ± 17.9% predicted. Abnormally low exercise capacity (peak rate of oxygen uptake < lower limit of normal) was present in 26%. Relative to peak power output, rate of oxygen uptake, and minute ventilation, 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 physiologic abnormalities during CPET.

Interpretation: 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.