This study examined the effects of menstrual cycle phase on ventilatory control. Fourteen eumenorrheic women were studied in the early follicular (FP; 1–6 days) and mid-luteal (LP; 20–24 days) phase of the menstrual cycle. Blood for the determination of arterial PCO2 (PaCO2 ), plasma strong ion difference ([SID]), progesterone ([P4]), and 17-estradiol ([E2]) concentrations were obtained at rest. Subjects performed a CO2 rebreathing procedure that included prior hyperventilation and maintenance of iso-oxia to evaluate central and peripheral chemoreflex, and nonchemoreflex drives to breathe. Resting PaCO2 and [SID] were lower; minute ventilation (˙VE), [P4] and [E2] were higher in the LP versus FP.
Within the LP, significant correlations were observed for PaCO2 with [P4], [E2] and [SID]. Menstrual cycle phase had no effect on the threshold or sensitivity of the central and/or peripheral ventilatory chemoreflex response to CO2. Both (˙VE) and the ventilatory response to hypocapnia (representing nonchemoreflex drives to breathe) were ∼1 L/min greater in the LP versus FP accounting for the reduction in PaCO2 . These data support the hypothesis that phasic menstrual cycle changes in PaCO2 may be due, at least in part, to the stimulatory effects of [P4], [E2] and [SID] on ventilatory drive.
For the full article, click here >> Phasic Menstrual Cycle Effects on the Control of Breathing in Healthy Women. Slatkovska. 2006