Medical & biological engineering & computing
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Med Biol Eng Comput · Jul 1997
Measurement of venous oxyhaemoglobin saturation in the adult human forearm by near infrared spectroscopy with venous occlusion.
Measurement of the oxygenation of the peripheral tissues provides useful information about tissue perfusion. A method is described for the measurement of peripheral venous oxyhaemaglobin saturation (SvO2) in the adult forearm by a noninvasive technique, near infrared spectroscopy (NIRS) with venous occlusion. A series of studies is performed on healthy adults to compare measurements of forearm SvO2 made by NIRS with measurements of superficial venous SvO2 made by co-oximetry, and to study the effect of different optode spacings. ⋯ This difference is likely to have been due to a more superficial volume of tissue being studied with the closer optode spacing. Peripheral SvO2 can be measured non-invasively using NIRS with venous occlusion. It may prove to be a useful method to study circulatory disturbances.
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Med Biol Eng Comput · Jul 1997
Optical assessment of recovery of tissue blood supply after removal of externally applied pressure.
The authors use photoelectric plethysmography to determine the external occlusion pressure for blood vessels in human tissue in vivo. Three wavelengths are employed; 950 nm (infra-red), 640 nm (red) and 583 nm (yellow). Each probe is applied in turn to one finger of each subject. ⋯ The mean (+/-standard deviation) occlusion pressures for all 13 subjects investigated are 7.1 (+/-1.9) kPa for infra-red, 6.3 (+/-1.7) kPa for red and 5.8 (+/-1.8) kPa for yellow. The pressure is 0.79 (+/-0.83) kPa lower for red compared with infra-red (P < 0.01), 0.54 (+/-0.60) kPa lower for yellow compared with red (P < 0.002) and 1.3 (+/-1.0) kPa lower for yellow compared with infra-red (P < 0.005). The reduced penetration of shorter optical wavelengths can be used to detect the lower occlusion pressures of the smaller blood vessels nearer the skin surface.