THE EFFECT OF MENSTRUATION ON THE PULMONARY CARBON-MONOXIDE DIFFUSING-CAPACITY

We studied variations in DL(co) during the menstrual cycle in 14 healt hy women with a mean age of 29 (SD, 7) yr. Eight were using oral contr aceptives, and six were not. DL(co) was determined 1 to 7 d before the onset of menses, daily during each of the first 4 d of menses, and 5 to in d after onset of menses. In both groups of subjects, the highest values for DL(co) were obtained before menses, the lowest were on the third day of menses, whereas after completion of menses the values in creased but were not as high as prior to menses. The mean DL(co) for a ll subjects was 23.1 (SD, 3.2) ml/min/mm Hg before menses, 20.9 (SD, 3 .0) on the third day of menstruation, and 21.6 (SD, 3.3) 5 to 10 d aft er onset of menses. The mean percent difference between DL(co) before and on the third day of menses in all 14 subjects was 9.2 (SD, 4.4)%. There were no significant changes in hemoglobin on these days to accou nt for the changes in DL(co). Pulmonary capillary blood volume determi ned in 10 of the subjects did not show a significant change. It is con cluded that DL(co) can vary significantly during the menstrual cycle, with the highest values occurring prior to menses and the lowest value s occurring on the third day of menses, with a mean difference between them of 9%. These variations need to be considered when evaluating DL (co) in female patients in the menstrual age group.