Development of a new instrument for non-invasive measurements of tissue (muscle) blood flow by near-infrared spectoroscopy.

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We have developed a method of non-invasive and continuous measurements of oxygen saturation (St O_2) and absolute volumes of hemoglobin (Hb vol) using near-infrared spectroscopy (NIRS). An instrument (PSA-III N) has been designed for the use of this method so that the tissue surface can be irradiated successively with infrared light of three wavelengths, and the scattered light from the tissue can be measured on the tissue surface at a point a certain distance away from the irradiated site. St O_2 and absolute values of Hb vol in tissues can be non-invasively determined from the measured absorbance using equations derived from Lambert-beer's law. Values of Hb vol from PSA-III N show the absolute values of Hb vol or blood vol in tissue. So, we applied to measure muscle-blood flow using PSA-III N.In generally, to measure the tissue-blood flow is doing by method of venous occlusion (60mmHg) plethysmography. So, we measured the tissue-blood flow using PSA-III N by venous occlusion (60mmHg). And we compared the values between from the usual method of venous occlusion (60mmHg) plethysmography and from the our PSA-III N with venous occlusion (60mmHg). 8 male subjects were used in this experiment. Each subject was conducted a graded handgrip exercise. During the exercise, muscle blood flow were measured by two methods , i.e., the usual method of venous occlusion (60mmHg) plethysmography and the method of PSA-III N with venous occlusion (60mmHg).We got total 203 points of muscle blood flow with the two methods. And a significant correlation (r=0.60, p<0.01) was observed between values from two methods.From these results, we concluded that the instrument (PSA-III N) offers a means of measuring muscle blood flow, and may be very useful in basic and clinical medicine.