Smielewski P, Czosnyka M, Pickard J D, Kirkpatrick P
Medical Research Council Cambridge Center for Brain Repair and Academic Neurosurgical Unit, Addenbrooke's Hospital, University of Cambridge UK.
Stroke. 1997 Feb;28(2):331-8. doi: 10.1161/01.str.28.2.331.
Near-infrared spectroscopy (NIRS) derives information about the concentrations of oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb) from measurements of light attenuation caused by these chromosphores. The aim of this study was to assess NIRS as a tool for testing CO2 reactivity in patients with carotid artery disease.
One hundred patients with symptomatic carotid occlusive disease were examined (age range, 44 to 83 years). The severity of stenosis ranged from 30% to 100% (median, 80%) on the ipsilateral side and 0% to 100% (median, 30%) on the contralateral side. Monitored parameters included transcranial Doppler flow velocity, changes in concentration of HbO2 and Hb, cutaneous laser-Doppler blood flow, endtidal CO2, arterial blood pressure, and arterial oxygen saturation. Hypercapnia was induced with the use of a 5% CO2/air mixture for inhalation. To estimate the contribution of skin flow to NIRS during reactivity testing, the superficial temporal artery was compressed, and the NIRS changes in response to the fall in laser-Doppler blood flow were recorded. Finally, reproducibility of reactivity testing was assessed in 10 patients who were subjected to repeated examinations over 3 days.
Flow velocity- and HbO2-derived reactivity values were related to the severity of the stenosis (P = .0001 and P = .017, respectively). The correlation between the two reactivity modalities was significant (r = .49, P < .000001). The median estimated contribution of skin flow to NIRS changes was 15.8%. Another variable affecting HbO2 signal changes during the CO2 challenge was arterial blood pressure (P = .025). Reproducibility of HbO2 reactivity was similar to flow velocity reactivity (14.3% and 18.6% variation, respectively).
NIRS shows potential as an alternative technique for testing CO2 reactivity in patients with carotid disease provided that conditions are carefully controlled. Marked changes in arterial blood pressure may render the NIRS reactivity indices unreliable, and the contribution from extracranial tissue must be taken into account when significant.
近红外光谱技术（NIRS）通过测量由氧合血红蛋白（HbO₂）和脱氧血红蛋白（Hb）这些发色团引起的光衰减来获取有关它们浓度的信息。本研究的目的是评估NIRS作为检测颈动脉疾病患者二氧化碳反应性的一种工具。
对100例有症状的颈动脉闭塞性疾病患者进行检查（年龄范围44至83岁）。同侧狭窄严重程度为30%至100%（中位数80%），对侧为0%至100%（中位数30%）。监测参数包括经颅多普勒血流速度、HbO₂和Hb浓度变化、皮肤激光多普勒血流、呼气末二氧化碳、动脉血压和动脉血氧饱和度。使用5%二氧化碳/空气混合气体吸入诱导高碳酸血症。为了评估反应性测试期间皮肤血流对NIRS的贡献，压迫颞浅动脉，并记录激光多普勒血流下降时NIRS的变化。最后，在10例患者中进行了3天的重复检查，以评估反应性测试的可重复性。
血流速度和HbO₂衍生的反应性值与狭窄严重程度相关（分别为P = 0.0001和P = 0.017）。两种反应性模式之间的相关性显著（r = 0.49，P < 0.000001）。皮肤血流对NIRS变化的估计中位数贡献为15.8%。二氧化碳激发试验期间影响HbO₂信号变化的另一个变量是动脉血压（P = 0.025）。HbO₂反应性的可重复性与血流速度反应性相似（分别为14.3%和18.6%的变化）。
只要条件得到仔细控制，NIRS显示出作为检测颈动脉疾病患者二氧化碳反应性的替代技术的潜力。动脉血压的显著变化可能使NIRS反应性指数不可靠，并且当颅外组织的贡献显著时必须予以考虑。
