Microcirculation plays an important role by supplying oxygen and nutrients to maintain our lives. It is known that, as pathogenesis of sepsis, the microcirculation is impaired at the early stage of sepsis. In this case, it is expected that thrombomodulin alfa (TM alfa) works for the recovery of microcirculation. Direct observation of the impairment and recovery of microcirculation related to sepsis may give us clear understanding of those phenomena. In this study, we conducted experiments to observe microcirculation of septic model rats with an optical system. In these experiments, by attaching a chamber to the back of each rat, the same region of the microcirculation was consecutively monitored. Then, these rats were divided into three groups: control model rats (sham group), septic model rats (diseased group), and septic model rats to which TM alfa was administered (treated group). Each group includes five rats. In the diseased group smaller vessels disappeared and larger vessels became thinner. On the other hand, the treated group showed at first the degradation of microcirculation then the recovery. This may indicate effectiveness of TM alfa. We also estimated the blood velocity and blood vessel diameter from the acquired motion pictures to evaluate condition of the microcirculation. As a result, we quantitatively confirmed while blood velocity and blood vessel diameter of the diseased group decreased, that of the treated group decreased and then recovered. It should be noted that the set of motion pictures obtained in these experiments has potentially useful information for further analysis and is to be open to relevant researchers.
Near-infrared spectroscopy (NIRS) is a noninvasive method for monitoring tissue oxygen saturation (StO2). Many commercial NIRS devices are presently available. However, the precision of those devices is relatively poor because they are using the reflectance-model with which it is difficult to obtain the blood volume and other unchanged components of the tissue. Human webbing is a thin part of the hand and suitable to measure spectral transmittance. In this paper, we present a method for measuring StO2 of human webbing from a transmissive continuous-wave nearinfrared spectroscopy (CW-NIRS) data. The method is based on the modified Beer-Lambert law (MBL) and it consists of two steps. In the first step, we give a pressure to the upstream region of the measurement point to perturb the concentration of deoxy- and oxy-hemoglobin as remaining the other components and measure the spectral signals. From the measured data, spectral absorbance due to the components other than hemoglobin is calculated. In the second step, spectral measurement is performed at arbitrary time instance and the spectral absorbance obtained in the step 1 is subtracted from the measured absorbance. The tissue oxygen saturation (StO2) is estimated from the remained data. The method was evaluated on an arterial occlusion test (AOT) and a venous occlusion test (VOT). In the evaluation experiment, we confirmed that reasonable values of StO2 were obtained by the proposed method.
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