Estimating Breathing Reserve at Peak Treadmill Exercise: Influence of Sex and Fitness

Abstract

Purpose: A low breathing reserve (peak ventilation [(VEpeak)-E-center dot]/estimated maximum ventilation [(VEmax)-E-center dot] <= 15%) is recommended as the decision node to indicate abnormal ventilatory limitation during incremental cycle ergometry. Given higher (VEpeak)-E-center dot 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 (VEmax)-E-center dot 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.