HYPOXIC VENTILATORY RESPONSE DURING SLEEP IN NORMAL PREMENOPAUSAL WOMEN

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Abstract
Sleep apnea syndromes and nonapneic arterial O2 desaturation during sleep are reported more commonly in men than in women. Because men have recently been shown to have a considerably reduced hypoxic ventilatory response (HVR) during sleep, it was questioned if this finding would apply to women as well. Accordingly, isocapnic hypoxic responsiveness was measured in 6 normal women during wakefulness and all stages of sleep during both follicular and luteal phases of the menstrual cycle. During non-REM [non-rapid-eye-movement] sleep, women were found to maintain their waking levels of HVR, measured as the slope of the relationship between ventilation and decreasing Hb saturation. Hypoxic ventilatory response fell to 70% of the awake value during REM sleep, which was a significant change (P < 0.05). Although HVR tended to be greater in the luteal than in the follicular phase of the menstrual cycle, both awake and asleep, this was significant only in stage-2 sleep (P < 0.05). When compared with recently reported men studies, these women demonstrated significantly less awake HVR even when corrected for body surface area (P < 0.05). During sleep men and women had similar hypoxic responses, although this represents a considerable decrement in the awake response in the men and little change in the women. The relationship of these findings to the observed sexual differences in sleep disordered breathing is speculative.