Bifurcation in blood oscillatory rhythms for patients with ischemic stroke:a small scale clinical trial using laser Doppler flowmetry and computational modelling of vasomotion

We describe application of spectral analysis of laser Doppler flowmetry (LDF) signals to investigation of cerebrovascular haemodynamics in patients with post-acute ischemic stroke (AIS) and cerebrovascular insufficiency. LDF was performed from 3 to 7 days after the onset of AIS on forehead in the right and left supraorbital regions in patients. Analysis of LDF signals showed that perfusion in the microvasculature in AIS patients was lower than that in patients with cerebrovascular insufficiency. As a result of wavelet analysis of the LDF signals we obtained activation of the vasomotion in the frequency range of myogenic oscillation of 0.1 Hz and predominantly nutritive regime microcirculation after systemic thrombolytic therapy of the AIS patients. In case of significant stroke size, myogenic activity and nutritive pattern microhaemodynamics were reduced, in some cases non-nutritive pattern and/or venular stasis was revealed. Wavelet analysis of the LDF signals also showed asymmetry in wavelet spectra of the LDF signals obtained in stroke-affected and unaffected hemispheres in the AIS patients. A mechanism underlying the observed asymmetry was analysed by computational modelling of vasomotion developed in (Arciero & Secomb, 2012). We applied this model to describe relaxation oscillation of arteriole diameter which is forced by myogenic oscillation induced by synchronous calcium oscillation in vascular smooth muscle cells. Calculation showed that vasomotion frequency spectrum at the low-frequency range (0.01 Hz) is reciprocally modulated by myogenic oscillation (0.1 Hz) that correlates with experimental observation of inter-hemispheric variation in the LDF spectrum

Wearable laser Doppler sensors for evaluating the nutritive and shunt blood flow

This study is devoted to the trials of wearable diagnostic system that implements the laser Doppler flowmetry technique to analyse the blood microcirculation. We do preliminary test with involvement of limited group of healthy volunteers of different age and in patients with type 2 diabetes. During the series of measurements, the microcirculation parameters was measured for 10 minutes in the palmar surfaces of the big toes and in the inner sides of the upper thirds of the shins. A statistically significant differences was found in bypass index, nutritive and shunt blood ow in shins between older group of volunteers and patients' group as well as in shunt blood flow in fingers between younger and older groups of volunteers

Detection of angiospastic disorders in the microcirculatory bed using laser diagnostics technologies

The evaluation of the microcirculatory bed functional state and the identification of angiospastic disorders with related complications, when the pathological changes are reversible, have an important role in medical practice. The aim of this study was to evaluate the possibility of using optical noninvasive methods and the cold pressor test to solve this problem. A total of 33 patients with rheumatological diseases and 32 healthy volunteers were included in the study. Laser Doppler flowmetry, tissue reflectance oximetry and pulse oximetry were used as optical noninvasive methods. The parameters were recorded before, immediately after and 20(Formula presented.)min after the cold pressor test. Based on the measured parameters, the complex parameters of the microcirculatory bed were calculated. A detailed statistical analysis of the parameter changes for each individual in the two groups displayed diverse microcirculatory bed parameter responses upon cold exposure, with differing recovery of parameters after CPT. New diagnostic criteria were proposed for the identification of angiospastic disorders. According to the proposed criteria, 27 people of the volunteers group were confirmed to not display any disorders. In the patient group, however, 18 people were observed to have a relatively normal functional state of the microcirculatory bed, while 15 people were observed to have a possible tendency to angiospasm. To highlight the differences between a relatively normal state and presence of angiospastic disorders, statistical analysis of experimental data was carried out, which revealed significant differences. Further analysis of data with angiospastic disorders identified a relationship between their diagnoses and the results of laboratory studies. Thus, the evaluation of combined noninvasive optical diagnostic method use, the cold pressor test and proposed diagnostic criteria showed a positive result. This approach can be used to detect the presence of possible angiospastic disorders and related complications, as well as microcirculatory bed disorders against the background of other diseases

Comparison of wearable and bedside laser Doppler flowmetry and fluorescence spectroscopy monitors

Advances in the development of ultra-compact semiconductor lasers have opened up new possibilities for the development of wearable devices implementing biophotonic technologies, such as laser Doppler flowmetry (LDF) and fluorescence spectroscopy (FS). This work is aimed to evaluate the correlation between diagnostic parameters simultaneously registered by a newly developed wearable device and a standard bedside fiber-based technique. Experimental studies with healthy volunteers using the occlusion test showed a high correlation between the parameters recorded by the two devices.,,,,,,,,

Laser Doppler flowmetry in blood and lymph monitoring, technical aspects and analysis

The aim of this work was to study the possibilities of the laser Doppler flowmetry method for the joint study of microhaemo- and lymph circulation of human skin. Conducting a series of experimental studies allowed to trace the relationship of recorded signals of microcirculation of blood flow and lymph flow, as well as to study their oscillation nature by using wavelet analysis

Multimodal optical measurement for study of lower limb tissue viability in patients with diabetes mellitus

According to the International Diabetes Federation, the challenge of early stage diagnosis and treatment effectiveness monitoring in diabetes is currently one of the highest priorities in modern healthcare. The potential of combined measurements of skin fluorescence and blood perfusion by the laser Doppler flowmetry method in diagnostics of low limb diabetes complications was evaluated. Using Monte Carlo probabilistic modeling, the diagnostic volume and depth of the diagnosis were evaluated. The experimental study involved 76 patients with type 2 diabetes mellitus. These patients were divided into two groups depending on the degree of complications. The control group consisted of 48 healthy volunteers. The local thermal stimulation was selected as a stimulus on the blood microcirculation system. The experimental studies have shown that diabetic patients have elevated values of normalized fluorescence amplitudes, as well as a lower perfusion response to local heating. In the group of people with diabetes with trophic ulcers, these parameters also significantly differ from the control and diabetes only groups. Thus, the intensity of skin fluorescence and level of tissue blood perfusion can act as markers for various degrees of complications from the beginning of diabetes to the formation of trophic ulcers

Determining the Regions for Efficient Use of Electro­jet Low­thrust Engines

This work addresses the issues on determining the optimal regions for using propulsion system for spacecraft at low near-Earth orbits. An analysis of spacecraft launches over the past 5 years has been performed. The result of analyzing the launches is the type of spacecraft, selected for subsequent calculations, specifically a remote sensing satellite at low near-Earth orbit. We have solved the problem on determining parameters for the trajectory of a spacecraft motion, exposed to external non-permanent forces. Based on an analysis of the external influence, the scope of possible future application of spacecraft propulsion systems has been defined. A comparative analysis has been performed for the mass criterion of efficiency of using propulsion systems based on the chemical mono-component and electro-jet engines in order to solve tasks on maintaining the circular orbit parameters over a long time.For orbit altitudes below 300 km, as was established based on the calculation results, the application of a propulsion system proved to be inefficient due to the need for a large reserve of fuel aboard and a large required engine thrust. For satellites at circular orbits from 350 to 450 km, a propulsion system that includes the Hall-effect- based engine ST-25, manufactured by SETS, proved to be more effective than the chemical propulsion unit. Application of chemical engines to maintain the orbit parameters at altitude above 500 km would be preferable to electro-jet ones due to a relatively small mass of the chemical propulsion system and a sufficient resource of engines operation in order to maintain the orbit.We have obtained parameters for the propulsion system that uses the Hall-effect-based engine ST-25 in order to maintain orbital parameters within different ranges of altitudes, solar activity, and geometrical parameters for a satellite. The result of calculation is the determined necessary resource of operation and the fuel stock to maintain parameters of the orbit.The calculation results obtained could be used to design new satellites and to modify satellite platforms

Interaction of supercavitating strikers with underwater obstacles

The interaction of supercavitating strikers with obstacles placed in water was investigated in a wide range of intersection angles. Several options of the interaction of strikers with obstacles are considered, including through puncturing, destruction of the striker, and ricochet. Estimation was made of the magnitude of the decrease in the speed of strikers in the cases of through puncturing and ricochet

Wearable sensors for blood perfusion monitoring in patients with diabetes mellitus

Abstract The rising interest in the development of new wearable electronic devices for mobile healthcare can be exemplified by great opportunities for the development of new methods for broader use of blood perfusion monitoring for the purposes of precision medicine. A fine analysis of capillary blood flow structure and its rhythmic oscillations in the time and frequency domains, coupled with a new possibility of round-the-clock monitoring, can provide valuable diagnostic information about the state of microvascular blood flow. In this chapter, we review recent advances in the development and clinical applications of a new class of wearable devices for blood perfusion monitoring and diagnosis of microvascular complications in type 2 diabetes