Pollard V, Prough D S, DeMelo A E, Deyo D J, Uchida T, Widman R
Department of Anesthesiology, University of Texas Medical Branch, Galveston 77555-0591, USA.
Anesth Analg. 1996 Feb;82(2):278-87. doi: 10.1097/00000539-199602000-00011.
Near-infrared spectroscopy may allow continuous and noninvasive monitoring of regional brain hemoglobin oxygen saturation by measuring the differential absorption of infrared light by oxyhemoglobin and deoxyhemoglobin. We have previously examined the correlation between the spectroscopic signal generated by a prototype cerebral oximeter (Invos 3100; Somanetics, Troy, MI), and global brain hemoglobin oxygen saturation calculated from arterial and jugular venous bulb oxygen saturations. Because the technology does not distinguish between arterial and venous hemoglobin saturation, changes in the proportion of cerebral arterial and venous blood volume, which may result from changes in blood flow or venous distending pressure, may confound measurements. In eight conscious volunteers breathing hypoxic oxygen mixtures, we examined the influence of supine, 20 degrees Trendelenburg, and 20 degrees reverse Trendelenburg positions on the correlation of the spectroscopic measurement of cerebral oxygen saturation in the field assessed by the probe (CSfO2) and the calculated brain hemoglobin oxygen saturation (CScombO2), estimated as 0.25 x arterial saturation plus 0.75 x jugular venous bulb oxygen saturation. We found that changes in position did not influence the association between CSfO2 and CScombO2 (r2 = 0.69-0.885) during hypoxic challenge. In a second set of eight volunteers, we studied the influence of hypercapnia and hypocapnia and body position on the association between CSfO2 and CScombO2, and found that they were less well correlated (r2 = 0.366-0.976) in individual patients. Because changes in body position and Paco2 confound the relationship between CSfO2 and CScombO2, changes in CSfO2 can best be assessed if position and Paco2 are constant.
近红外光谱法可通过测量氧合血红蛋白和脱氧血红蛋白对红外光的吸收差异，实现对局部脑血红蛋白氧饱和度的连续无创监测。我们之前曾研究过一种原型脑血氧饱和度仪（Invos 3100；Somanetics公司，密歇根州特洛伊市）产生的光谱信号与根据动脉和颈静脉球部血氧饱和度计算得出的全脑血红蛋白氧饱和度之间的相关性。由于该技术无法区分动脉血和静脉血的血红蛋白饱和度，血流量或静脉扩张压力变化可能导致的脑动脉血和静脉血容量比例变化，可能会干扰测量结果。在8名呼吸低氧混合气体的清醒志愿者中，我们研究了仰卧位、头低脚高20度和头高脚低20度体位对探头所测脑氧饱和度（CSfO2）与计算得出的脑血红蛋白氧饱和度（CScombO2，估计为0.25×动脉血氧饱和度 + 0.75×颈静脉球部血氧饱和度）光谱测量相关性的影响。我们发现，在低氧刺激期间，体位变化并未影响CSfO2与CScombO2之间的相关性（r2 = 0.69 - 0.885）。在另一组8名志愿者中，我们研究了高碳酸血症、低碳酸血症和体位对CSfO2与CScombO2之间相关性的影响，发现个体患者中它们的相关性较差（r2 = 0.366 - 0.976）。由于体位和动脉血二氧化碳分压（Paco2）的变化会混淆CSfO2与CScombO2之间的关系，因此在体位和Paco2保持恒定的情况下，才能最好地评估CSfO2的变化。
