Distribution of blood flow oscillation across the Doppler shift evaluated by the proposed approach with local pressure test.

A step-wise increase in local pressure is known to cause a gradual change in the parameters of capillary blood flow in the
upper layers of the skin, and can also affect the measurement results of various optical methods. The impact of the procedure has several subsequent effects, such as mechanical compression of vessels, and neurological and metabolic compensating mechanisms like pressure-induced vasodilation, which maintain the homeostasis of the skin during moderate levels of external pressure and tissue hypoxia. To examine how those effects are translated to the blood flow registering in different ranges of the Doppler spectra, we have developed a 3D-printed pressure distribution tool compatible with the developed sensor which was used, and equipped with a set of weights. 

During the main series of measurements, the weights were placed into the PDT in a step-wise manner to achieve the
following values of pressure applied: 10 mmHg, 30 mmHg, 90 mmHg, 150 mmHg, 210 mmHg. At the end of the procedure, the load was reduced back to 30 mmHg. Experiments were conducted with the participation of 7 healthy volunteers with 10 min LDF recording for each step. To estimate the prominence of the observed effects and substantiate the measuring routing, several preliminary experiments were also conducted where the set of values of pressure was applied with a step-wise increase and then decrease with about 2 min of LDF recordings for each step.

Published in IEEE Transactions on Biomedical Engineering "Diagnosis of skin vascular complications revealed by time-frequency analysis and laser Doppler spectrum decomposition", Zherebtsov et al.

已知局部压力的阶梯式升高会导致皮肤表层毛细血管血流参数发生渐进式变化，同时还会对多种光学检测方法的测量结果产生影响。该施压过程的影响存在一系列后续效应，例如血管的机械压迫，以及诸如压力诱导性血管舒张这类神经与代谢代偿机制——在中等程度外压与组织缺氧状态下，这类机制可维持皮肤的稳态。为探究这些效应如何体现在不同多普勒频谱范围下的血流记录中，我们研发了一款与本次实验所用传感器相适配的3D打印压力分布装置（pressure distribution tool, PDT），并为其配备了一组配重砝码。

在主测量序列中，我们以阶梯式方式将砝码置入PDT，以实现如下施加压力值：10 mmHg、30 mmHg、90 mmHg、150 mmHg、210 mmHg。实验结束后，将负载降至30 mmHg。本次实验共有7名健康志愿者参与，每个压力步骤均进行10分钟的激光多普勒血流仪（Laser Doppler Flowmetry, LDF）记录。为评估所观测效应的显著性并验证测量流程的合理性，我们还开展了若干预实验：在预实验中，压力值以阶梯式升高后再降低的方式施加，每个步骤的LDF记录时长约为2分钟。

本研究成果发表于《IEEE生物医学工程汇刊（IEEE Transactions on Biomedical Engineering）》，论文题为《基于时频分析与激光多普勒频谱分解的皮肤血管并发症诊断（Diagnosis of skin vascular complications revealed by time-frequency analysis and laser Doppler spectrum decomposition）》，作者为Zherebtsov等人。