Changes in Exhaled Carbon Dioxide during the Menstrual Cycle and Menopause

Introduction: The menstrual cycle (MC) reflects multifaceted hormonal changes influencing women’s metabolism, making it a key aspect of women’s health. Changes in hormonal levels throughout the MC have been demonstrated to influence various physiological parameters, including exhaled carbon dioxide (CO2). Lumen is a small handheld device that measures metabolic fuel usage via exhaled CO2. This study leverages exhaled CO2 patterns measured by the Lumen device to elucidate metabolic variations during the MC, which may hold significance for fertility management. Additionally, CO2 changes are explored in menopausal women with and without hormonal replacement therapy (HRT). Methods: This retrospective cohort study analyzed exhaled CO2 data from 3,981 Lumen users, including eumenorrheal women and menopausal women with and without HRT. Linear mixed models assessed both CO2 changes of eumenorrheal women during the MC phases and compared between menopausal women with or without HRT. Results: Eumenorrheic women displayed cyclical CO2 patterns during the MC, characterized by elevated levels during the menstrual, estrogenic and ovulation phases and decreased levels during post-ovulation and pre-menstrual phases. Notably, despite variations in cycle length affecting the timing of maximum and minimum CO2 levels within a cycle, the overall pattern remained consistent. Furthermore, CO2 levels in menopausal women without HRT differed significantly from those with HRT, which showed lower levels. Conclusion: This study reveals distinct CO2 patterns across MC phases, providing insights into hormonal influences on metabolic activity. Menopausal women exhibit altered CO2 profiles in relation to the use or absence of HRT. CO2 monitoring emerges as a potential tool for tracking the MC and understanding metabolic changes during menopause. © 2024 The Author(s).