髄液中Progesteroneの妊婦の換気におよぼす影響

Influence of progesterone in the CSF on the ventilation in pregnant women

　今世紀当初より妊娠中に換気量が増加することが観察されており^1,2），Hasselbalchら^3）のhormoneとの関係を示唆する報告以来，progesterone （以下prog．）が呼吸中枢に作用することによると考えられているが^4,5），その機序は未だ解明されていない。

　本研究は血液および，より中枢の情報を反映すると思われる脳脊髄液（以下CSF）中のprog．濃度と，酸塩基平衡からみた卵胞期から産褥期に至る換気量の変化との関係を臨床例で検討した。

The influence of progesterone in the cerebrospinal fluid (CSF) and the plasma on the arterial Pco₂ was studied in 27 women, aged 23-50 yr, who had undergone operations. They were divided into four groups : follicular phase, luteal phase, late pregnan-cy, and puerperium. There was a positive correla-tion (p<0.001) between plasma and CSF in pro-gesterone. The CSF/plasma ratio of the progeste-rone decreased from 0.08 at the follicular phase to 0.02 at late pregnancy. These progesterone concent-rations in CSF were enough for physiological activity to occur at the luteal phase and during pregnancy. There was a significant correlation (p <O. 01) be-tween the increase of progesterone in plasma and the drop of arterial Pco₂. However, the progeste-rone in CSF was not correlated significantly with arterial Pco₂. The ratio of the decrease of arterial Pco₂ to the increase of plasma progesterone from the follicular phase to the luteal phase was much larger than that from the luteal phase to the late pregnancy. That is, the ventilatory response to pro-gesterone during pregnancy was worse than the other phase. On the other hand, CSF acid-base balance adapted to the hypocapnia and CSF pH did not change from the follicular phase at the luteal phase, however, CSF pH rose significantly (p <0.001) in comparison with the follicular phase at late pregnancy. Because the decrease in bicar-bonate did not correspond to the drop in Pco₂. It is thought that these changes in CSF acid-base bal-ance depressed the central chemosensitive area at late pregnancy. In conclusion, it seems that the CSF progesterone transferred from blood effects to the respiratory center, however, the hyperventilation during pregnancy can not be explained only by the increase of the progesterone in plasma or CSF.