Milani M; Hasselt University, REVAL/BIOMED, Hasselt, Belgium (
Milani JGPO; Machado FVC; Cipriano GFB;et al

Journal of Cardiopulmonary Rehabilitation & Prevention. 46(1):35-43, 2026

PURPOSE: A low breathing reserve (peak ventilation [Epeak]/estimated
maximum ventilation [Emax] <= 15%) is recommended as the decision node to
indicate abnormal ventilatory limitation during incremental cycle
ergometry. Given higher Epeak during weight-bearing exercise, we aim to
establish which coefficients should multiply the forced expiratory volume
in 1 second (FEV1) to reduce the prevalence of a low breathing reserve in
healthy subjects undergoing treadmill exercise.

METHODS: We determined the coefficients for FEV1 multiplication
associated with <5% prevalence of a low breathing reserve in 3544 healthy
individuals aged 20 to 80 years. We then contrasted their performance in
differentiating healthy subjects (N = 148) from patients with chronic
obstructive pulmonary disease (COPD) (N = 133) in an external validation
sample.

RESULTS: A low breathing reserve was found in 22% and 6% of women versus
48% and 17% of men when FEV1 was multiplied by 35 and 40, respectively.
Sex-adjusted coefficients required to decrease the prevalence of a low
breathing reserve ranged from 33 and 48 in women versus 36.5 and 50 in men
in those showing peak oxygen uptake <80% and >120% predicted,
respectively. Breathing reserve using the new sex- and fitness-adjusted
coefficients were superior to previous values in differentiating health
from disease, regardless of COPD severity.

CONCLUSION: Higher coefficients for FEV1 multiplication are required to
estimate Emax at peak treadmill exercise in men than in women, increasing
as a function of cardiorespiratory fitness in both sexes. These data are
poised to improve the yield of cardiopulmonary exercise tests in
accurately indicating pathological ventilatory limitation in patients with
respiratory diseases.