プレチモグラフ法の比較的研究

Critical Studies on Various Plethysmograp-hic Methods, with special reference to the "Reflexion Photoelectric Plethysmograph".

I．緒言

　皮膚の血流研究には多くの方法があるが，その変化を微細に且つ連続的に追求出来るものは，Plathysmograph（以下Plとす）であつて，現在最も多く採用されている。この内最も古くからあるものは機械的な方法で，普通指尖に適用されることが多いが^1-5）前腕においても工夫考案され，これに静脈閉塞法を加えて，その部の血流の絶対値をしらべ，興味ある成績があげられている^4）。容器内腔の体積変化を記録するのにも，また較正をするためにも種々の考案がなされている。しかるに光電管の発見以来，血液と他組織との一定波長の光の吸収度の差異を利用した光電Plの使用が盛んになり，これにCR結合の増幅器を連結して指尖脈波が記録されるようになつた。

　これに透過式^6-12）と反射式^13,14）があり，前者の方が指尖などでは感度をあげ易いために多く用いられているが，組織の厚い部分では使用し得ない欠点を有する。Hertzman^14），長谷川^13）は反射光電式のものを考案して，身体皮膚表面のあらゆる部分の容積変化を記録出来るようにした。一般には，これに連結する増幅器にはCR結合を用いて，脈波の振幅からその部の血流量を推定している。それは脈波の大きさと基線動揺との間には0.6，血量変化との間には0.86の相関があることを利用している^9）。

"Reflection Photoelectric Plethysmograph" -RPP-, which was early designed by Hertzman and modified By Hasegawa were applied through well stabilized DC amplifier chiefly on the finger and forearm in order to compare with the records simultaneously taken by means of various other plethysmographic mehtods. There was no discrepancy among these methods in relation to time coures and in magnitude of spontaneous or vasomotor fluctuations.

Number of capillary loops of finger nail-bed which could be observed under dermatoscope decreased in response to some mechanical stimulations proportionally with the declination of the level in RPP curve. The level fluctuation and pulse amplitude in RPP curve faded on with lesser intensity of illumination onto the skin, yet held a similarity to the curve recorded by ordinary intensity of illumination. The results above stated led us a conclusion that the records obtained by means of RPP represented chiefly the features of capillary vessels in superficial layer in the skin.

The slower fluctuations of the level in RPP curve which would be obtained thraugh the DC amplifier were eliminated completely with the use of the amplifier of a smaller time constant of 0.05 sec., but the curve lining the tops of the pulse wave represented ordinarilly a similar fluctu-ation to the level fluctuation in the records due to DC amplifier, only with exception in the case of venous occlusion. From these results the simultaneous plethysmographic recording by means of RPP with DC and RC (time constant 0.05sec.) amplifier may possibly reveal some details con-cerning the vascular responses in the skin.

The expense of this work were defrayed by a grant from the Ministry of Education.