Non-Invasive Study of Tissue Oxygen Metabolism Using Near Infrared laser Light ; Toward its Clinical Application

为了监测人脑的氧合状态，研制了一种新型便携式高性能近红外激光光谱仪。使用780、805和830 nm三种不同波长的近红外激光，每束激光通过光纤束交替照射头部。通过光电倍增管或硅胶光电二极管检测组织反射或透过的光量。光电二极管的输出信号由微型计算机处理，并根据我们实验室建立的方程实时记录计算的氧合、脱氧和总(氧合)脱氧血红蛋白(Hb)值的时间过程。通过大鼠头的活体实验验证了计算公式的可靠性和可接受性。对20例体外循环患者在反射式模式下进行近红外监测。结果表明，在目前的CPB技术中，体外循环期间脑氧合水平维持在生理范围内，脑血容量的变化与泵流量平衡相吻合。也就是说，在体外循环期间，脑氧合水平在平均灌流压高于60毫米汞柱的情况下基本保持恒定，而在低于50毫米汞的情况下，观察到血红蛋白氧合的进行性下降。这些发现使我们得出结论，使用近红外光对脑氧合进行非侵入性监测可以在床边提供关于组织新陈代谢的有价值的数据，并允许适当地处理危重患者。该系统有待解决的问题包括：1)对脑氧合和血容量的变化进行绝对量化，2)临床引入细胞色素氧化酶氧化还原测量系统，以获得有关脑细胞功能的信息，以及3)对迄今获得的近红外信息进行进一步的临床评估。

A new protable high performance apparatus for near infrared (NIR) laser spectrophotometry was developed to monitor the oxygenation state in human brain. Three different wavelengths of 780, 805 and 830nm of the NIR laser beam were used and each laser light illuminated alternatively the head through a fiber optic bundle. The amount of light reflected by or transmitted from the tissue was detected by the photomultiplier or silicone photodiode. The output signals of the photodiode were processed by a microcomputer, and the time course of calculated oxy, deoxy and total (oxy^+deoxy) hemoglobin (Hb) values were recorded in real time using the equations developed in our lavoratory. The calculation equations were verified in vivo with the rat head to confirm the reliability and acceptability of our methodology. NIR monitring was applied to 20 cases of cardiopulmonaly bypass patients in reflectance mode. The results demonstrated that in current CPB technique, the cerebral oxygenation levels during the bypass were maintained within the physiological range and the changes en the brain blood volume corresponded well to the pump flow balance. That is, the brain oxygenaation level was maintained roughly constant at a mean perfusion pressure of over 60mmHg during CPB, whereas below 50mmHg, a progressive decline in the Hb oxygenation was observed. These findings led us to conclude that non-invasive monitoring of cerebral oxygenation using NIR light can provide valuable data at the bed side about tissue metabolism and allow for the proper management of critical patients.The problems that remain to be solved with this system include : 1) the absolute quantification of the changes in cerebral oxygenation and blood volume, 2) clinical introduction of a cytochrome oxidase redox measuring system to obtain information concerning ; the brain cell functions directory and 3) a further clinical evaluation of NIR informations obtained so far.