Reflex hypoxic drive to respiration during the menstrual cycle

Area of Science:

• Physiology
• Respiratory Control
• Women's Health

Background:

• The menstrual cycle involves hormonal fluctuations, notably progesterone, which can affect respiratory regulation.
• Previous research suggests progesterone influences ventilation, but its specific impact on reflex hypoxic drive is not fully understood.

Purpose of the Study:

• To investigate the effect of the menstrual phase on reflex hypoxic drive in women.
• To determine if hormonal changes during the luteal phase alter the hypoxic ventilatory response.

Main Methods:

• Studied 9 women, measuring maximal fall in ventilation (VE) during 20-second oxygen breathing.
• Assessed reflex hypoxic drive as a percentage of resting VE.
• Compared measurements between the follicular and luteal phases of the menstrual cycle.

Main Results:

• Resting end-tidal oxygen (PAO2) was higher and end-tidal carbon dioxide (PACO2) was lower in the luteal phase.
• Despite altered alveolar gases, reflex hypoxic drive was significantly greater in the luteal phase (14.4%) compared to the follicular phase (9.3%).
• Resting VE was 7.8% higher in the luteal phase, with augmented hypoxic drive contributing substantially (59%) to this increase.

Conclusions:

• Progesterone-induced hyperventilation during the luteal phase is partly mediated by an increased reflex hypoxic drive.
• This augmented hypoxic drive appears to be centrally regulated, even under conditions of hyperoxia and hypocapnia.
• The contribution of increased hypoxic drive to resting ventilation shows significant inter-individual variability.