Peltier stackを利用した電極による皮膚血流量連続測定の試み

Measurement of skin blood flow using the electrode with Peltier stack

　レイノー症候群などの四肢の末梢循環障害の診断において，持続的に手指などの局所の皮膚血流量をモニターすることは，皮膚温の持続モニターとともに大変有用である。今まで用いられてきた血流測定法の一つに熱クリアランスの原理を用いた熱拡散法がある。この方法は不活化ガスを用いたガスクリアランス法やアイソトープクリアランス法などと比較して，血流の変化に対して敏感に反応し，持続的にモニターしうるという利点はあるが，基線の動揺が大きく安定性に欠けるため，定性的変化をとらえるにはよいが，定量化できないという欠点を有していた。この欠点を除くため，Brawley^1）は電極にPeltier stack利用することにより基線の良好な安定を得た。Carter^2〜4）は，これを¹³³Xeを用いたアイソトープクリアランス法で絶対値較正を行い，熱拡散法による脳血流量の連続測定として報告している。我々は，皮膚血流量測定においてPeltier stackを利用した電極の有用性を検討するために皮膚組織の代表として指の皮膚を選び血流量測定に関する基礎的研究を行った。同時に本電極を用いて測定した指血流量を絶対値として表示するため，吸入式水素クリアランス法による測定値との比較検討を行い有意の相関関係を得たので，ここに報告する。

We have measured human finger blood flow by thermal diffusion method using the electrode with Peltier stack. Fundamental studies including comparison of fin-ger blood flow measured by this method (thermal FBF) and that by hydrogen clearance method (hydrogen FBF) were carried out. The thermal diffusion flow probe was placed on the back of the right middle finger. It consisted of two L-shaped gold plates : one was heated, and the other was cooled by Peltier stack when a current was applied. The thermocouples were installed in two gold plates and it produced a voltage difference of the order of hundred of microvolts.

At rest, the voltage difference of the thermocouples (V) was 461.7±3.1mV (MEAN±SEM). It rapidly increaced and reached to 486.3±1.9 mV (MEAN+ SEM) by finger ischemia, when the pneumatic tourni-quet was inflated to 300mmHg. And then it returned to the level at rest by deflation of the pneumatic tourni-quet to 0 mmHg. The result indicated that the voltage difference of the thermocouples varied with finger blood flow.

A highly significant positive correlation was obtained between 1/V and hydrogen FBF (r=0.9646, p<0.001). The voltage difference of the thermocouples with no flow (V₀) and constant K were estimated, and the calibration line was determined. This line is based on the equation : F=K(1/V-1/V₀)A highly significant positive correlation was obtained between thermal FBF and hydrogen FBF (r=0.9645, p<0.001).

Using thermal diffusion method calibrated previously by hydrogen clearance method in the normal human subjects, the absolute value of FBF can be measured continuously and noninvasively in human. It is con-cluded that finger blood flow measurement by thermal diffusion method was applied to diagnosis of circulation disorder of the fingers.