Ferreira Leonardo F, Koga Shunsaku, Barstow Thomas J
Department of Anatomy and Physiology and Kinesiology, Kansas State University, Manhattan, KS 66506-0302, USA.
J Appl Physiol (1985). 2007 Dec;103(6):1999-2004. doi: 10.1152/japplphysiol.01414.2006. Epub 2007 Sep 6.
Utilization of near-infrared spectroscopy (NIRS) in clinical exercise testing to detect microvascular abnormalities requires characterization of the responses in healthy individuals and theoretical foundation for data interpretation. We examined the profile of the deoxygenated hemoglobin signal from NIRS {deoxygenated hemoglobin + myoglobin [deoxy-(Hb+Mb)] approximately O(2) extraction} during ramp exercise to test the hypothesis that the increase in estimated O(2) extraction would be close to hyperbolic, reflecting a linear relationship between muscle blood flow (Q(m)) and muscle oxygen uptake (Vo(2)(m)) with a positive Q(m) intercept. Fifteen subjects (age 24 +/- 5 yr) performed incremental ramp exercise to fatigue (15-35 W/min). The deoxy-(Hb+Mb) response, measured by NIRS, was fitted by a hyperbolic function [f(x) = ax/(b + x), where a is the asymptotic value and b is the x value that yields 50% of the total amplitude] and sigmoidal function {f(x) = f(0) + A/[1 + e(-(-c+dx))], where f(0) is baseline, A is total amplitude, and c is a constant dependent on d, the slope of the sigmoid}, and the goodness of fit was determined by F test. Only one subject demonstrated a hyperbolic increase in deoxy-(Hb+Mb) (a = 170%, b = 193 W), whereas 14 subjects displayed a sigmoidal increase in deoxy-(Hb+Mb) (f(0) = -7 +/- 7%, A = 118 +/- 16%, c = 3.25 +/- 1.14, and d = 0.03 +/- 0.01). Computer simulations revealed that sigmoidal increases in deoxy-(Hb+Mb) reflect a nonlinear relationship between microvascular Q(m) and Vo(2)(m) during incremental ramp exercise. The mechanistic implications of our findings are that, in most healthy subjects, Q(m) increased at a faster rate than Vo(2)(m) early in the exercise test and slowed progressively as maximal work rate was approached.
在临床运动测试中利用近红外光谱（NIRS）检测微血管异常，需要了解健康个体的反应特征并为数据解读建立理论基础。我们在递增运动期间检查了NIRS的脱氧血红蛋白信号特征{脱氧血红蛋白+肌红蛋白[脱氧 - （Hb + Mb）]近似于O₂提取}，以检验以下假设：估计的O₂提取增加将接近双曲线，反映肌肉血流量（Qm）与肌肉摄氧量（Vo₂（m））之间的线性关系，且Qm截距为正。15名受试者（年龄24±5岁）进行递增斜坡运动直至疲劳（15 - 35 W/分钟）。通过NIRS测量的脱氧 - （Hb + Mb）反应由双曲线函数[f（x）= ax /（b + x），其中a是渐近值，b是产生总幅度50％的x值]和S形函数{f（x）= f（0）+ A / [1 + e^（-（-c + dx））]，其中f（0）是基线，A是总幅度，c是取决于d的常数，d是S形曲线的斜率}拟合，拟合优度通过F检验确定。只有一名受试者表现出脱氧 - （Hb + Mb）呈双曲线增加（a = 170％，b = 193 W），而14名受试者表现出脱氧 - （Hb + Mb）呈S形增加（f（0）= -7±7％，A = 118±16％，c = 3.25±1.14，d = 0.03±0.01）。计算机模拟显示，在递增斜坡运动期间，脱氧 - （Hb + Mb）的S形增加反映了微血管Qm与Vo₂（m）之间的非线性关系。我们研究结果的机制意义在于，在大多数健康受试者中，在运动测试早期Qm的增加速率比Vo₂（m）快，并在接近最大工作速率时逐渐减慢。
