Ekstrom M;  Respiratory Medicine, Lund University, Lund, Sweden.
Li PZ; Bourbeau J; Tan WC; Jensen D

Chest. 169(2):449-461, 2026 Feb.

BACKGROUND: Breathlessness on exertion is a common, distressing, and
limiting symptom that can be quantified on incremental cardiopulmonary
exercise testing (CPET) using normative reference equations.

RESEARCH QUESTION: Is the breathlessness abnormality best uncovered and
assessed at symptom limitation (peak exercise) compared with submaximal
exercise intensities?

STUDY DESIGN AND METHODS: 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.

RESULTS: 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.

INTERPRETATION: 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.