Levy W J, Levin S, Chance B
Department of Anesthesia, University of Pennsylvania School of Medicine, Philadelphia 19104-4283, USA.
Anesthesiology. 1995 Oct;83(4):738-46. doi: 10.1097/00000542-199510000-00013.
The application of phase-modulated near-infrared techniques for measurement of the oxygen saturation of cerebral tissue requires both validation by conventional measures of cerebral oxygenation and determination of normal and abnormal values. This study was undertaken to validate phase-modulated near-infrared measurements of cerebral oxygen saturation by comparing them with electroencephalographic evidence of cerebral ischemia during implantation of cardioverting defibrillators. This comparison also yields an estimate of the ischemic threshold as measured with near-infrared techniques.
Electroencephalograms and near-infrared measurements were performed during 85 episodes of ventricular fibrillation in ten patients. Light at 754, 785, and 816 nm was modulated at 200 MHz, transmitted through the skull, and the path lengths of the reflected light were determined by measuring the phase shifts. The electroencephalogram was inspected for changes during the hypotension associated with the arrhythmia and the oxygen saturation was calculated from the near-infrared path lengths. Changes in oxygen saturation were then compared with electroencephalographic evidence of cerebral ischemia.
The mean saturation before fibrillation was 56.5% +/- 1.2 (SEM). In 40 (47%) of the events, electroencephalographic evidence of ischemia was observed. Such changes were related to the minimum saturation observed during ventricular fibrillation (44% +/- 2.5 vs. 56% +/- 1.9 in the absence of electroencephalographic changes; P < 0.001). The ischemic threshold was estimated to be 47% saturation. The sensitivity of this technique was estimated to be 0.6, the specificity 0.84, and the predictive accuracy 0.73.
Near-infrared measurements reflect changes in cerebral oxygenation as indicated by electroencephalographic evidence of cerebral ischemia.
应用相位调制近红外技术测量脑组织氧饱和度，既需要通过传统的脑氧合测量方法进行验证，也需要确定正常和异常值。本研究旨在通过将相位调制近红外测量的脑氧饱和度与心脏复律除颤器植入过程中脑缺血的脑电图证据进行比较，来验证该测量方法。这种比较还能得出用近红外技术测量的缺血阈值。
对10例患者的85次室颤发作进行了脑电图和近红外测量。754、785和816nm的光以200MHz进行调制，透过颅骨传输，并通过测量相移来确定反射光的光程。检查心律失常相关低血压期间脑电图的变化，并根据近红外光程计算氧饱和度。然后将氧饱和度的变化与脑缺血的脑电图证据进行比较。
室颤前的平均饱和度为56.5%±1.2（标准误）。在40次（47%）事件中，观察到脑缺血的脑电图证据。这些变化与室颤期间观察到的最低饱和度有关（无脑电图变化时为44%±2.5，有脑电图变化时为56%±1.9；P<0.001）。缺血阈值估计为饱和度47%。该技术的敏感性估计为0.6，特异性为0.84，预测准确性为0.73。
近红外测量反映了脑缺血脑电图证据所表明的脑氧合变化。
