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首页> 外文会议>Conference on Advanced Biomedical and Clinical Diagnostic Systems II; 20040125-20040126; San Jose,CA; US >In vivo measurements of the influence of the skin on cerebral oxygenation changes measured with Near Infrared Spectrophotometry (NIRS)
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In vivo measurements of the influence of the skin on cerebral oxygenation changes measured with Near Infrared Spectrophotometry (NIRS)

机译：使用近红外分光光度法（NIRS）进行的皮肤对脑氧合变化影响的体内测量

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Goal: To investigate the influence of skin on the accuracy and precision of regional cerebral oxygenation measurements using CW-NIRS and to reduce the inter individual variability of NIRS measurements by normalization with data from an extra wavelength. Method: Three piglets (7.8-9.3 kg) were anesthetized, paralyzed and mechanically ventilated. Receiving optodes were placed over the left and right hemisphere (C_3, C_4 EEG placement code) and one emitting optode on C_z position (optode distance= 1.8cm). Optical densities (OD) were measured for 3 wavelengths (767, 850, 905 nm) (OXYMON) during stable normoxic, mild and deep hypoxemic conditions (SaO_2=100%, 80% and 60%) of one minute in each region. This was repeated 3 times: all optodes with skin (condition 1); one receiving optode directly on the skull (2); emitting and also receiving optode on the skull (3). The absolute cO_2Hb, cHHb, ctHb concentrations (μmol/L) were calculated from the OD's and changes with respect to the SaO_2=100% condition were estimated. Because ODs varied over a large range, the light intensity was externally attenuated to adapt to the range of the spectrophotometer. The data were then corrected for these attenuation effects and for pathlength changes caused by skin removal using the OD at the independent wavelength (λ=975nm). Results: Removal of the skin resulted in an increase of the absorption values (average 0.25 OD in condition 2 and 0.42 OD in condition 3 with respect to condition 1). The change from normoxic to medium, and to deep hypoxic conditions produced a decrease of cO_2Hb (-15, and -29 μmol/L, respectively), an increase in cHHb (+16, and +35 μmol/L) and in ctHb (+1, and +5 μmol/L). Total skin removal yielded an extra change in cO_2Hb (-5, -1 μmol/L), cHHb (+8, +9 μmol/L), and ctHb (+3, +8 μmol /L). The coefficient of variability of the absolute concentration changes was considerably decreased by the normalization of densities by the density obtained at 795 nm. Conclusion: Skin and subcutaneous layers influence the regional oxygenation measurements but the estimated concentration changes are dominated by changes of the oxygenation levels in the brain. Inter individual variability can be considerably reduced by the normalization.
机译：目的：研究皮肤对使用CW-NIRS进行的区域性大脑氧合测量的准确性和精密度的影响，并通过使用额外波长的数据进行归一化来减少NIRS测量的个体间差异。方法：麻醉三只小猪（7.8-9.3 kg），使其瘫痪并进行机械通气。接收光电二极管放置在左右半球上（C_3，C_4 EEG放置代码），一个发射光电二极管位于C_z位置（光电二极管距离= 1.8cm）。在每个区域一分钟的正常常氧，轻度和深度低氧血症条件下（SaO_2 = 100％，80％和60％），在3个波长（767、850、905 nm）（OXYMON）上测量了光密度（OD）。重复3次：所有的光电二极管都带有皮肤（条件1）；一个接收光电二极管直接在头骨上（2）；在头骨上发射并接收optode（3）。根据OD值计算出绝对的cO_2Hb，cHHb，ctHb浓度（μmol/ L），并估计了相对于SaO_2 = 100％条件的变化。由于OD在较大范围内变化，因此光强度从外部衰减以适应分光光度计的范围。然后针对这些衰减效应以及由于使用独立波长（λ= 975nm）的OD去除皮肤而导致的路径长度变化对数据进行校正。结果：去除皮肤导致吸收值增加（条件2相对于条件1的平均OD为0.25，条件3的平均值为OD 0.42）。从常氧到中等，再到深氧不足的变化，导致cO_2Hb降低（分别为-15和-29μmol/ L），cHHb（分别为+16和+35μmol/ L）和ctHb升高（ +1和+5μmol/ L）。完全去除皮肤后，cO_2Hb（-5，-1μmol/ L），cHHb（+8，+9μmol/ L）和ctHb（+3，+8μmol/ L）发生了额外变化。通过以795nm获得的密度对密度进行归一化，绝对浓度变化的变异系数大大降低。结论：皮肤和皮下层会影响区域的氧合测量，但估计的浓度变化主要由大脑氧合水平的变化决定。个体间的变异性可以通过归一化大大降低。

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