Changes of ventilation and ventilatory response to hypoxia during the menstrual cycle

The relationship between change in hypoxic sensitivity in respiration, defined as increment in ventilation per drop of arterial O₂ saturation, with the phase change from follicular to luteal and those in resting pulmonary ventilation, mean inspiratory flow (V_T/T_I), alveolar partial pressures of CO₂ and O₂ ( and, respectively) and body temperature was studied in 10 women. There was a significant relationship between % increase in hypoxic sensitivity and decrement of resting that occurred in the luteal phase. However, no significant relationships were observed between change in hypoxic sensitivity and those in the remaining parameters studied. The intersubject variation in % increase in resting during the luteal phase was not associated with that in % increase in hypoxic sensitivity. The results indicate that the contribution of increased hypoxic sensitivity to increasing during the luteal phase is variable among subjects. Reasons for the increase in hypoxic sensitivity with hypocapnia are discussed.