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.
Microcirculation plays an important role in maintaining our lives. Observing the microcirculation has been considered important in understanding the disease mechanisms and diagnosing diseases. Sidestream dark-field (SDF) imaging is one of the methods to observe the microcirculation. However, the SDF imaging has several problems for instance artifacts caused by pressure and heat. Measurement points is under pressure because SDF imaging requires direct contact with measurement points, which may affect hemodynamics. Therefore, we construct a non-contact setup. Furthermore, at the early stage of sepsis, it is known that the microcirculation is impaired. To investigate the relationship between the flow of red blood cells (RBCs) and septic shock, we conducted an experiment using the setup to observe septic model rats and sham rats. Moreover, we calculated the blood velocity to estimate the flow of RBCs by using acquired motion pictures. We confirmed that the sham rats showed slight change in lactate value during the observation and improved the blood velocity compared with just after abdominal closure. However, lactate value of the septic model rats increased and the blood velocity of septic model rats decreased. This finding suggests that microcirculatory alteration may be a sign of sepsis and septic shock progression.
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.
The sidestream dark-field (SDF) imaging allows direct visualization of red blood cells in microvessels near tissue surfaces. We have developed an image-based oximetry method using two-band images obtained by SDF imaging (SDF oximetry) and a trial SDF device with light-emitting diodes to obtain band images. In this study, we propose a technique of producing oxygen saturation (SO2) maps from SDF images and perform animal experiments in vivo. To produce SO2 maps, we use spectral analysis using two band images obtained with our SDF device. As an image processing, the combination of both the Hessian-based and pixel value-based techniques as blood vessel extraction from an SDF image is used. From the experiment with the surface of rat small intestines, we can produce SO2 maps and find that the map represents arterioles and venules those were determined based on the blood ow from SDF images. Moreover, we find the variation of SO2 along a blood vessel running direction.