HYPERCAPNIC BLOOD-PRESSURE RESPONSE IS GREATER DURING THE LUTEAL-PHASE OF THE MENSTRUAL-CYCLE

We investigated the cardiovascular responses to acute hypercapnia duri ng the menstrual cycle. Eleven female subjects with regular menstrual cycles performed hypercapnic rebreathing tests during the follicular a nd luteal phases of their menstrual cycles. Ventilatory and cardiovasc ular variables were recorded breath by breath. Serum progesterone and estradiol were measured on each occasion, Serum progesterone was highe r during the luteal [50.4 +/- 9.6 (SE) nmol/l] than during the follicu lar phase (2.1 +/- 0.7 nmol/l; P < 0.001), but serum estradiol did not differ (follicular phase, 324 +/- 101 pmol/l; luteal phase, 162 +/- 7 1 pmol/l; P = 0.61). The systolic blood pressure responses during hype rcapnia were 2.0 +/- 0.3 and 4.0 +/- 0.5 mmHg/Torr (1 Torr = 1 mmHg ri se in end-tidal Pco(2)) during the follicular and luteal phases, respe ctively, of the menstrual cycle (P < 0.01). The diastolic blood pressu re responses were 1.1 +/- 0.2 and 2.1 +/- 0.3 mmHg/Torr during the fol licular and luteal phases, respectively (P < 0.002). Heart rate respon ses did not differ during the luteal (1.7 +/- 0.3 beats . min(-1). Tor r(-1)) and follicular phases (1.4 +/- 0.3 beats . min(-1). Torr(-1); P = 0.59). These data demonstrate a greater presser response during the luteal phase of the menstrual cycle that may be related to higher ser um progesterone concentrations.