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The effect of menstrual cycle phase on diffusing capacity of the lung Bacon, Catherine


Pulmonary diffusing capacity (D[sub L]) has been observed to decrease during menses. Nonetheless, a descriptive study of alterations in this parameter with menstrual cycle phase has not been completed and the mechanism of change is not clear. Changes in resting single-breath diffusing capacity of carbon monoxide (D[sub L[sub CO]]), and in its two components: pulmonary capillary blood volume (V[sub C]), and membrane diffusing capacity (D[sub M]) were measured in 13 normally menstruating women at points within the menstrual cycle chosen to best discriminate between the effects of oestradiol, progesterone and prostaglandins. In addition, haemoglobin concentration ([Hb]), packed cell volume (PCV), and percent of carboxyhaemoglobin (COHb) were measured. Measurements of D[sub L[sub CO]], V[sub C], D[sub M], and [Hb] were undertaken at five testing points throughout three menstrual cycles, whilst COHb and PCV were assessed at four points within one cycle. The phase of the menstrual cycle was determined by quantitative analysis of basal body temperature recorded daily by subjects. No changes in resting D[sub L[sub CO]], D[sub L[sub CO]] divided by alveolar volume (V[sub A]), COHb, PCV or for [Hb] corrected D[sub L[sub CO]], D[sub L[sub CO]]/ V[sub A], D[sub M] or V[sub C] were found using one-way repeated measures analyses of variance (ANOVAs) of the most representative ovulatory menstrual cycle for each subject. Two-way repeated measures ANOVAs of D[sub L[sub CO]] and D[sub L[sub CO]]/V[sub A]; and [Hb] corrected D[sub L[sub CO]] and D[sub L[sub CO]]/V[sub A], which separated the effects of the five testing points and the ovulatory or anovulatory status of a menstrual cycle were also performed and no significant changes were observed. When the effect of the large hormonal differences between an ovulatory and an anovulatory cycle were removed, a trend towards an increase in DL independent of the effects of [Hb] at mid-cycle and during the luteal phase compared to the early follicular phase were observed. Notwithstanding the extreme variability of hormonal changes within the human menstrual cycle, without the benefit of hormonal analysis we have not found consistent alterations in D[sub L[sub CO]] with menstrual phase in normally menstruating women. This is despite careful effort to time diffusion test with points in the cycle that should best discriminate between the hormonal effects of oestradiol, progesterone and prostaglandins.

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