Cejnar M, Kobler H, Hunyor S N
Department of Cardiology, Royal North Shore Hospital, St Leonard's (Sydney), Australia.
J Biomed Eng. 1993 Mar;15(2):151-4. doi: 10.1016/0141-5425(93)90047-3.
Finger blood volume is commonly determined from measurement of infra-red (IR) light transmittance using the Lambert-Beer law of light absorption derived for use in non-scattering media, even when such transmission involves light scatter around the phalangeal bone. Simultaneous IR transmittance and finger volume were measured over the full dynamic range of vascular volumes in seven subjects and outcomes compared with data fitted according to the Lambert-Beer exponential function and an inverse function derived for light attenuation by scattering materials. Curves were fitted by the least-squares method and goodness of fit was compared using standard errors of estimate (SEE). The inverse function gave a better data fit in six of the subjects: mean SEE 1.9 (SD 0.7, range 0.7-2.8) and 4.6 (2.2, 2.0-8.0) respectively (p < 0.02, paired t-test). Thus, when relating IR transmittance to blood volume, as occurs in the finger during measurements of arterial compliance, an inverse function derived from a model of light attenuation by scattering media gives more accurate results than the traditional exponential fit.
即使手指血容量的测量涉及围绕指骨的光散射，通常仍使用源自非散射介质的朗伯-比尔光吸收定律，通过测量红外（IR）光透射率来确定。在七名受试者的血管容量全动态范围内，同时测量了红外透射率和手指容积，并将结果与根据朗伯-比尔指数函数和由散射材料引起的光衰减推导的反函数拟合的数据进行了比较。通过最小二乘法拟合曲线，并使用估计标准误差（SEE）比较拟合优度。反函数在六名受试者中给出了更好的数据拟合：平均SEE分别为1.9（标准差0.7，范围0.7 - 2.8）和4.6（2.2，2.0 - 8.0）（p < 0.02，配对t检验）。因此，在将红外透射率与血容量相关联时，如在测量动脉顺应性期间手指中发生的情况，由散射介质光衰减模型推导的反函数比传统的指数拟合给出更准确的结果。
