Blood Pulsation Research Articles

Assessment of the long-term trend in angiodystonic syndrome of the upper extremities in stage I vibration disease using the ultrasound method

Introduction. Diseases of the upper extremities caused by exposure to local vibration at the workplace are a ubiquitous problem. These diseases occur or are aggravated by exposure to vibration at the workplace when using vibration-hazardous equipment. Purpose of the study – is to identify the features of upper limb angiodystonic syndrome in vibration disease at stage I, depending on work experience. Materials and methods. Ultrasound scanning of the arteries of the upper extremities was performed in seventy patients. Spectral and velocity indices such as resistance index (RI), diastolic blood flow rate (V ED), systolic (pulse) blood flow rate (V PS) and pulsation index (PI) were measured in the distal part of the forearm. Results. Upon contact with a vibration tool, for each year of work experience, the systolic (pulse) blood flow rate (V PS) in the radial and left ulnar arteries significantly were found to decrease by an average of 0.57–0.58 (p<0.05). In the ulnar artery, PI increases on average by 0.03–0.062, but the changes are not statistically significant (p>0.05). With an increase in the length of service by 1 year, the RI in the left radial and ulnar arteries significantly increases by 0.0003–0.0012 (p<0.05). Limitations of the study. The main disadvantages of ultrasound are the long-term and operator-dependent method. Conclusion. With an increase in work experience, the indices characterizing angiodistonic disorders: pulsation index (PI), resistance index (RI) – significantly increase with each year of experience when exposed to local vibration. This can be used for differential diagnosis of peripheral angiodistonic upper limb syndrome of occupational etiology, in particular, vibration disease associated with exposure to local vibration at stage 1. With an increase in work experience, the indices characterizing angiodistonic disorders: pulsation index (PI), resistance index (RI) – significantly elevate with each year of experience when exposed to local vibration. As part of the ultrasound screening study, scanning of the arteries of the upper extremities in patients at the clinic of occupational pathology can be performed at the preclinical stage to prevent prolonged chronic ischemia of the upper extremities. This diagnostic method can be especially valuable in differentiating peripheral angiodistonic upper limb syndrome of occupational etiology, in particular, vibration disease at the stage 1.

What Remote PPG Oximetry Tells Us about Pulsatile Volume?

While pulse oximetry using remote photoplethysmography (rPPG) is used in medicine and consumer health, sound theoretical foundations for this methodology are not established. Similarly to traditional pulse oximetry, rPPG oximetry uses two wavelengths to calculate the tissue oxygenation using the so-called ratio-of-ratios, R. However, the relationship between R and tissue oxygenation has not been derived analytically. As such, rPPG oximetry relies mostly on empirical methods. This article aimed to build theoretical foundations for pulse oximetry in rPPG geometry. Using the perturbation approach in diffuse approximation for light propagation in tissues, we obtained an explicit expression of the AC/DC ratio for the rPPG signal. Based on this ratio, the explicit expression for "ratio-of-ratios" was obtained. We have simulated the dependence of "ratio-of-ratios" on arterial blood saturation across a wide range (SaO2 = 70-100%) for several commonly used R/IR light sources (660/780, 660/840, 660/880, and 660/940 nm) and found that the obtained relationship can be modeled by linear functions with an extremely good fit (R2 = 0.98-0.99) for all considered R/IR pairs. Moreover, the location of the pulsatile volume can be extracted from rPPG data. From experimental data, we found that the depth of blood pulsations in the human forehead can be estimated as 0.6 mm on the arterial side, which points to the papillary dermis/subpapillary vascular plexus origin of the pulsatile volume.

Computing pulsatile blood flow of coronary artery under incomplete boundary conditions

BackgroundAccurate measurement of pulsatile blood flow in the coronary arteries enables coronary wave intensity analysis, which can serve as an indicator for assessing coronary artery physiology and myocardial viability. Computational fluid dynamics (CFD) methods integrating coronary angiography images and fractional flow reserve (FFR) offer a novel approach for computing mean coronary blood flow. However, previous methods neglect the inertial effect of blood flow, which may have great impact on pulsatile blood flow calculation. To improve the accuracy of pulsatile blood flow calculation, a novel CFD based method considering the inertia term is proposed. MethodsA flow resistance model based on Pressure-Flow vs.Time curves is proposed to model the resistance of the epicardial artery. The parameters of the flow resistance model can be fitted from the simulated pulsating flow rates and pressure drops of a specific mode. Then, pulsating blood flow can be calculated by combining the incomplete pressure boundary conditions under pulsating conditions which are easily obtained in clinic. Through simulation experiments, the effectiveness of the proposed method is validated in idealized and reconstructed 3D model of coronary artery. The impacts of key parameters for generating the simulated pulsating flow rates and pressure drops on the accuracy of pulsatile blood flow calculation are also investigated. ResultsFor the idealized model, the previously proposed Pressure-Flow model has a significant leading effect on the computed blood flow waveform in the moderate model, and this leading effect disappears with the increase of the degree of stenosis. The improved model proposed in this paper has no leading effect, the root mean square error (RMSE) of the proposed model is low (the left coronary mode:≤0.0160, the right coronary mode:≤0.0065) for all simulated models, and the RMSE decreases with an increase of stenosis. The RMSE is consistently small (≤0.0217) as the key parameters of the proposed method vary in a large range. It is verified in the reconstructed model that the proposed model significantly reduces the RMSE of patients with moderate stenosis (the Pressure-Flow model:≤0.0683, the Pressure-Flow vs.Time model:≤0.0297), and the obtained blood flow waveform has a higher coincidence with the simulated reference waveform. ConclusionsThis paper confirms that ignoring the effect of inertia term can significantly affect the accuracy of calculating pulsatile blood flow in moderate stenosis lesions, and the new method proposed in this paper can significantly improves the accuracy of calculating pulsatile blood flow in moderate stenosis lesions. The proposed method provides a convenient clinical method for obtaining pressure-synchronized blood flow, which is expected to facilitate the application of waveform analysis in the diagnosis of coronary artery disease.

Experimental study on real-time detection of artificial blood vessel micro-leakage via triboelectrification effect

Artificial blood vessels are prone to breakage in the form of apertures or fractures during periodic blood pulsation and installation. It has caused great threats and hidden danger to the treatment and rehabilitation of patients. Therefore, it is of great research value and practical significance to develop a rapid real-time detection method with high detection accuracy and good response characteristics for artificial blood vessels. Based on the triboelectrification(TE) effect and fluid boundary layer theory, this paper proposes and systematically studies a liquid–solid contact single-electrode mode sensing device for micro-leakage detection of vascular prosthesis (MLDVP). By real-time monitoring and analyzing the voltage and frequency characteristics of the output electrical signal, the damage form prediction, damage degree estimation, and leakage area location can be carried out quickly and effectively. The results show that the boundary layer structure and velocity gradient of the inner wall of the tube change when the artificial blood vessel is damaged, which changes the directional movement law of carriers at the liquid–solid interface, resulting in slow growth of the output open-circuit voltage. Further research shows that under the same damage type, with the gradual increase of damage degree, the output current of the external circuit detected by the system decreases gradually, and the corresponding output voltage change ratio also decreases. Therefore, the real-time monitoring and analysis of the open-circuit voltage and short-circuit current output by MLDVP can effectively realize the rapid detection and estimation of the damage location, damage type, and damage degree of the artificial blood vessel.

An in silico analysis of unsteady flow structures in a microaxial blood pump under a pulsating rotation speed

Background and objectiveVentricular assist devices (VADs) are generally designed to perform continuous flow. However, it has been proven that continuous flow, which is not a physiological hemodynamic state, may cause severe complications such as gastrointestinal bleeding, pulmonary hypertension, and ventricular suction. For these reasons, many pulsating blood pump control strategies have been proposed and have the potential for application in percutaneous ventricular assist devices (pVADs) or microaxial blood pumps. A few cases report extra hemolysis when introducing pulsating speed, while none involve blood pumps. This research's primary purpose is to evaluate the potential hemolysis of pVAD under pulsating flow conditions. MethodsFirst, the pulsating flow state is deduced using a heart failure model and varying speed. The heart model is established according to the pathology state collected from a clinical check. The rotation speed and boundary physical state are set to fit the heart failure model. The computational fluid dynamics (CFD) method with the hemolysis prediction model is performed. Furthermore, we used proper orthogonal decomposition (POD) analysis to reconstruct the flow field and obtain more details about shearing and transporting effects. Results(1) As a variable rotational speed was introduced, no significant gain in hemolysis accumulation appeared in pVAD. This is quite different from long-term implantable VADs. (2) Pulsation affects hemolysis mainly through pressure (or normal stress). Variable rotational speed affects hemolysis mainly through flow instability. (3) Variable rotational speed will increase the instability and influence hemolysis by transporting and shearing effects, while the transporting effect is more significant. ConclusionsThe unsteady flow state will affect the spatial distribution of hemolysis, which should be taken into account during control strategy and impeller shape design.

Analysis of physiological pulsating flow of fractional Maxwell fluid in a locally narrow artery

The purpose of this paper is to provide a novel reference for the early diagnosis and treatment of atherosclerosis. Two-dimensional governing equations of fractional-order Maxwell fluid flow in a local stenotic artery are established, taking real physiological pulsating blood flow at inlet into consideration. Drawing support from the finite difference method as well as the L1 formula, vorticity and stream functions are introduced to acquire numerical solutions for velocity, stream function, and pressure. The distribution of blood flow in narrowed arteries within a real physiological pulse cycle is discussed. Furthermore, the influences of the degree of stenosis δ, the stenosis length parameter L0, fractional order parameter α, and relaxation time λ on crucial medical indicators, including the time average of the wall shear stress, oscillatory shear index, relative residence time, and pressure distribution are revealed. The results show that the deceleration and reversal phases of real physiological pulsatile flow critically affect the progression of arterial stenosis, and increasing the fractional order parameter α weakens the development of stenosis, while increasing λ has the opposite effect. This study is expected to serve as a reference for formulating standards of key medical indicators in the early diagnosis of vascular stenosis.

WITHDRAWN: Appendiceal bleeding caused by vascular malformation: A case report and literature review

Introduction and importanceAcute lower gastrointestinal bleeding (LGIB) is common in clinical practice, however, appendiceal bleeding is extremely rare, which easy to be missed and misdiagnosed. Case presentationWe presented a case of a 33-year-old female who complained of hematochezia that had lasted for 1 day, colonoscopy showed continuous bleeding in the appendiceal orifice. A laparoscopic appendectomy was performed immediately, a pulsating blood vessel can be seen in the mesangium of the appendix, accordingly, active bleeding into the appendicular lumen was considered. Appendiceal pathology showed a large number of hyperplastic vessels were seen in the appendix mucosa and capillary vessels were dilated. Clinical conclusionAppendiceal bleeding is rare, lack of related guidelines and consensus, the preoperative detection of appendiceal bleeding is often challenging. Colonoscopy is extremely important, bowel preparation is not recommended for patients with acute LGIB routinely or only low-dose bowel preparation is recommended. Laparoscopic appendectomy is the most appropriate treatment for appendiceal bleeding. DiscussionIn our case, we provided the relevant data of computed tomography (CT), colonoscopy, pathology and laparoscopic surgery, and analysed the appendiceal bleeding caused by vascular malformation, to provide clinical experience.

Analysis of periodic pulsating blood flow of fractional Maxwell power-law fluid in carotid artery with elastic vessel wall

Hemodynamic analysis reveals a highly significant effect on the prevention, diagnosis, and treatment of human vascular diseases. This article goes deeply into the periodic pulsatile blood flow in the carotid artery with an elastic vessel wall. In view of blood rheological experimental data, the constitutive equation of fractional Maxwell power-law fluid with yield stress, which can describe the four characteristics of yield stress, viscoelasticity, shear thinning, and thixotropy is established. Meanwhile, drawing support from the data of pulsatile flow, the finite Fourier series of pressure gradient with a period of 1 s has been proposed. Leading into Hooke’s law can build the fluid-structure coupling boundary condition of blood flow and elastic vessel wall. The numerical solutions are got hold of finite difference method integrated with the newly developed L1-algorithm, and their convergence and stability of which are verified. The axial velocities of blood under different constitutive relationships are compared. The results throw light that other constitutive relationships underestimate the velocity of blood. Furthermore, the flow rate and wall shear stress on different fluid are calculated. It can be concluded that compared with Bingham fluid, the maximum and minimum flow rate/wall shear stress of fractional Maxwell power-law fluid with yield stress increases by 19% and 32%, respectively. The flow rate lags behind the pressure gradient and has time delay effect, on the contrary, the velocity of blood vessel wall is keeping pace with the pressure gradient. The effects of relevant physical parameters on velocity are discussed. In addition, the spatiotemporal distribution of blood flow in cerebral artery and femoral artery are analyzed.

Hands-free continuous carotid Doppler ultrasound for detection of the pulse during cardiac arrest in a porcine model

Background/PurposePulse palpation is an unreliable method for diagnosing cardiac arrest. To address this limitation, continuous hemodynamic monitoring may be a viable solution. Therefore, we developed a novel, hands-free Doppler system, RescueDoppler, to detect the pulse continuously in the carotid artery. MethodsIn twelve pigs, we evaluated RescueDoppleŕs potential to measure blood flow velocity in three situations where pulse palpation of the carotid artery was insufficient: (1) systolic blood pressure below 60 mmHg, (2) ventricular fibrillation (VF) and (3) pulseless electrical activity (PEA). (1) Low blood pressure was induced using a Fogarty balloon catheter to occlude the inferior vena cava. (2) An implantable cardioverter-defibrillator induced VF. (3) Myocardial infarction after microembolization of the left coronary artery caused True-PEA. Invasive blood pressure was measured in the contralateral carotid artery. Time-averaged blood flow velocity (TAV) in the carotid artery was related to mean arterial pressure (MAP) in a linear mixed model. ResultsRescueDoppler identified pulsatile blood flow in 41/41 events with systolic blood pressure below 60 mmHg, with lowest blood pressure of 19 mmHg. In addition the absence of spontaneous circulation was identified in 21/21 VF events and true PEA in 2/2 events. The intraclass correlation coefficient within animals for TAV and MAP was 0.94 (95% CI. 0.85–0.98). ConclusionsIn a porcine model, RescueDoppler reliably identified pulsative blood flow with blood pressures below 60 mmHg. During VF and PEA, circulatory arrest was rapidly and accurately demonstrated. RescueDoppler could potentially replace unreliable pulse palpation during cardiac arrest and cardiopulmonary resuscitation.

Hemodynamic study of blood flow in the aorta during the interventional robot treatment using fluid–structure interaction

An interventional robot is a means for vascular diagnosis and treatment, and it can perform dredging, releasing drug and operating. Normal hemodynamic indicators are a prerequisite for the application of interventional robots. The current hemodynamic research is limited to the absence of interventional devices or interventional devices in fixed positions. Considering the coupling effect of blood, vessels and robots, based on the bi-directional fluid–structure interaction, using the computational fluid dynamics and particle image velocimetry methods, combined with the sliding and moving mesh technologies, we theoretically and experimentally study the hemodynamic indicators such as blood flow lines, blood pressure, equivalent stress, deformation and wall shear stress of blood vessels when the robot precesses, rotates or does not intervene in the pulsating blood flow. The results show that the intervention of the robot increase the blood flow rate, blood pressure, equivalent stress and deformation of the vessels by 76.4%, 55.4%, 76.5%, and 346%, respectively. The operating mode of the robot during low-speed operation has little impact on the hemodynamic indicators. Using the methyl silicone oil as the experimental fluid, the elastic silicone pipe as the experimental pipe, and the intervention robot having a bioplastic outer shell, the velocity of the fluid around the robot is measured on the developed experimental device for fluid flow field in a pulsating flow when the robot runs. The experimental results are similar to the numerical results. Our work provides an important reference for the hemodynamic study and optimization of the mobile interventional devices.

Ультразвукові критерії затримки росту плода при передчасних пологах

Purpose - to increase the effectiveness of forecasting and early diagnosis of fetal growth retardation (FGR) in premature pregnancy on the basis of ultrasound examination. Materials and methods. 165 pregnant women were examined: 30 patients with an uncomplicated pregnancy that ended in physiological timely delivery - the control group (CG); 45 patients with premature birth (PB) (the Group I); 45 women with full-term pregnancy and FGR (the Group II) and 45 patients with PB and FGR (the Group III). Ultrasound examination included serial dynamic fetometry and placentography, dopplerography of vessels of the umbilical cord, ductus venosus, middle cerebral artery and fetal aorta with determination of systolic blood flow velocity and systolic peak velocity of blood flow, systolic-diastolic ratio, index resistance and pulsation index. Statistical processing of research results was carried out using standard programs «Microsoft Excel 5.0» and «Statistica 8.0». Results. А significant decrease in the parameters of the biparietal size of the fetal head in pregnant women of the Group III was detected at 24-25 weeks of pregnancy: in the CG - 66.4±0.65 mm, in the Group III - 65.02±0.31 mm (p<0.05), in the Group II - 66.2±0.46 mm. A more pronounced slowdown in the rate of growth of the biparietal size of the fetal head was found in pregnant women at 28-29 weeks of gestation, when a significant decrease (p<0.05) in its growth rate was observed in pregnant women of the Groups II and III. The peculiarities of the formation and functioning of the fetoplacental complex in this Groups were characterised by impaired fetal haemodynamics: increase in blood circulation velocity in the venous duct - 74.43±2.24 cm/s vs. 46.54±1.62 cm/s, respectively; p<0.05; increase in pulsatile index in the uterine artery - 1.611±0.04 vs. 1.424±0.07; p<0.05, and in the middle cerebral artery - 1.527±0.02 vs. 1.251±0.03; p<0.005, indicating the tension of subcompensatory reactions. Conclusions. Ultrasound feto- and placentametry in pregnant women with premature births against the backdrop of FGR showed that in patients with premature births, statistically significant deviations in the size of the fetus and placenta are observed from 24-25 weeks of gestation. Disruption of fetal hemodynamics is indicated by a significant increase in the speed of blood circulation in the ductus venosus in the Groups II and III (74.43±2.24 cm/s vs. 46.54±1.62 cm/s; p<0.05). The research was carried out in accordance with the principles of the Helsinki Declaration. The study protocol was approved by the Local Ethics Committee of the participating institution. The informed consent of the patient was obtained for conducting the studies. No conflict of interests was declared by the authors.

DETERMINING THE AMOUNT OF OXYGEN IN THE BLOOD BY A NONINVASIVE METHOD

Photoplethysmogram is used in medicine to monitor several diseases in a basic and convenient way. The object of research is a pulse oximeter - a device that measures the concentration of noninvasive hemoglobin in the blood and pulse ratios, based on the recording of a photoplethysmogram from a tool placed on the fingertip. This method is used in anesthesiology, resuscitation departments and operating rooms, is widely used in pulmonology departments, therapy and cardiology. In addition, the pulse oximeter goes beyond medicine and is used successfully in sports, games, professional fields, and so on. In the ultimate qualification work, existing methods of heart rate determination (pulse), based upon the method of photoplethysmography, which formed the basis for the development, was considered. This non-invasive method, formed on studying the absorption of light passing through the tissue site with pulsating blood, is simple and convenient. It is intended to operate this device, available to a wide range of users, both in monitoring vital signs and early diagnosis of diseases, and in self-monitoring and training. Keywords: Pulse oximetry, heart rate, non-invasive

Ultrasonic measurement of carotid luminal surface roughness with removal of axial displacement caused by blood pulsation

For early diagnosis of atherosclerosis, we have developed a method to measure the initial minute surface roughness utilizing the natural longitudinal displacement of the intima-media-complex (IMC) on the carotid artery caused by pulsation. However, the IMC displaces not only in the longitudinal direction but also in the axial direction due to the pulsation. In the present paper, we proposed a novel method to remove the pulsation component by spatially convolving a high-pass filter with the measured depths of IMC in the longitudinal direction. The proposed method was validated by a phantom experiment, and the surface roughness with ten saw teeth was correctly measured. Next, the surface roughness of the carotid artery wall was measured for two healthy volunteers. The proposed method reduced the variation of measured surface roughness among beams compared to the previous method.

Printed soft skin electrodes for seamless bio-impedance measurements

Bio-impedance measurements are widely used to assess various physiological parameters. Contemporary skin electrodes for bio-impedance measurements are cumbersome and novel electrode designs are needed to allow fast and easy placement, long-term stability and user comfort. This investigation introduces dry, printed, bio-compatible electrode arrays, made of screen-printed carbon and inkjet-printed PEDOT:PSS that measure bio-impedance non-invasively and stably. Two contact impedance measurements yield the lowest normalized values of soft electrodes reported to date. Four contact bio-impedance measurements from the radial, ulnar, common carotid and superficial temporal arteries were performed, demonstrating the ability to capture blood pulsation in different areas with small form factor. Owing to the unique properties of the printed electrodes reported here, we were able to demonstrate for the first time blood pulsation in the face, continuous blood pulsation measurement during simultaneous muscle activation and signal stability over many hours.

Mathematical Model and Simulation of Blood Flow Dynamics in Renal Interlobar Artery of Patients with Human immunodeficiency Virus

Mathematical models were developed considering wall movement, blood pulsation and flow dynamics of the blood in the interlobar artery. The formulated models were based on the fact that the motion of blood vessel wall is not only influenced by pulsation, but also other physiological processes like heartbeat, breathing, and body posture. The Newton’s second Law of motion was employed in assembling the forces acting on the interlobar artery. The wall shear stress (WSS) was studied alongside, arterial walls to study the actual flow dynamics and investigate the blood flow behaviour. The results of the study were presented on both two – dimensional (2D) and three (3D) – dimensional graphs showing a more realistic interaction between the arterial wall and the blood flow in patients with HIV/AIDS. It was deduced that the blood flow velocity decreased with time across the varying frequency from 0.20Hz to 0.50Hz in the interlobar arterial channel.

Modeling and computation for unsteady blood flow and solute concentration in a constricted porous artery

<abstract> <p>We investigated a physical system for unsteady blood flow and solute transport in a section of a constricted porous artery. The aim of this study was to determine effects of hematocrit, stenosis, pulse oscillation, diffusion, convection and chemical reaction on the solute transport. The significance of this study was uncovering combined roles played by stenosis height, hematocrit, pulse oscillation period, reactive rate, blood speed, blood pressure force and radial and axial extent of the porous artery on the solute transported by the blood flow in the described porous artery. We used both analytical and computational methods to determine blood flow quantities and solute transport for different parametric values of the described physical system. We found that solute transport increases with increasing stenosis height, blood pulsation period, convection and blood pressure force. However, transportation of solute reduces with increasing hematocrit, chemical reactive rate and radial or axial distance.</p> </abstract>

Flexible photoplethysmographic sensing devices for intelligent medical treatment

The beat frequency, flow rate, and oxygen content of human pulsating blood are important health indicators.

On‐Desk Model‐Based Study for Evaluating the Effect of Squeezing the Arteries in the Forearm on the Bioimpedance and Pressure of Blood

Background. Today, central aortic pressure (CAP) is measured through the invasive procedure of angiography. The only feasible alternative is applanation tonometry, requiring experienced staff to perform reliable measurements. The method of measuring the electrical bioimpedance (EBI) from the wrist gives promising results in estimating the CAP. However, the origin of the EBI data, its quality, and approaches to acquiring the signal are still vague. This study is aimed at determining the dependency of EBI of blood on the diameter, branching, and hindering the blood flow by squeezing the vessel. Methods. An on‐desk hydraulic and mechanical pipe system that imitates the arterial tree in the forearm with the modulated flow of saline solution to imitate the pulsating blood was constructed. The setup was verified in the simulation model. The flexible and rigid pipes were squeezed at selected locations of radial and ulnar arteries, and the superficial palmar arc and the pressure with impedance were measured. Results. The multifaceted effect of squeezing the selected locations of arteries in the forearm on the measured EBI and pressure was verified. The effect of arterial stiffening was verified, revealing a very strong inverse correlation of the time‐varying impedance (ΔZ(t)) of rigid pipe compared to the measured data of the wrist. Conclusion. To gain the highest magnitude of ΔZ(t), our research suggests applying pressure on the radial artery and measuring the EBI of the ulnar artery. Our results propose physiology‐based suggestions to increase the sensitivity of measured EBI of the pulse wave, constituting a base for designing novel wearable monitoring devices and algorithms for CAP estimation.

A mathematical framework for the dynamic interaction of pulsatile blood, brain, and cerebrospinal fluid

BackgroundShedding light on less-known aspects of intracranial fluid dynamics may be helpful to understand the hydrocephalus mechanism. The present study suggests a mathematical framework based on in vivo inputs to compare the dynamic interaction of pulsatile blood, brain, and cerebrospinal fluid (CSF) between the healthy subject and the hydrocephalus patient. MethodThe input data for the mathematical formulations was pulsatile blood velocity, which was measured using cine PC-MRI. Tube law was used to transfer the created deformation by blood pulsation in the vessel circumference to the brain domain. The pulsatile deformation of brain tissue with respect to time was calculated and considered to be inlet velocity in the CSF domain. The governing equations in all three domains were continuity, Navier-Stokes, and concentration. We used Darcy law with defined permeability and diffusivity values to define the material properties in the brain. ResultsWe validated the preciseness of the CSF velocity and pressure through the mathematical formulations with cine PC-MRI velocity, experimental ICP, and FSI simulated velocity and pressure. We used the analysis of dimensionless numbers including Reynolds, Womersley, Hartmann, and Peclet to evaluate the characteristics of the intracranial fluid flow. In the mid-systole phase of a cardiac cycle, CSF velocity had the maximum value and CSF pressure had the minimum value. The maximum and amplitude of CSF pressure, as well as CSF stroke volume, were calculated and compared between the healthy subject and the hydrocephalus patient. ConclusionThe present in vivo-based mathematical framework has the potential to gain insight into the less-known points in the physiological function of intracranial fluid dynamics and the hydrocephalus mechanism.

Beyond Human Touch Perception: An Adaptive Robotic Skin Based on Gallium Microgranules for Pressure Sensory Augmentation.

Robotic skin with human-skin-like sensing ability holds immense potential in various fields such as robotics, prosthetics, healthcare, and industries. To catch up with human skin, numerous studies are underway on pressure sensors integrated on robotic skin to improve the sensitivity and detection range. However, due to the trade-off between them, existing pressure sensors have achieved only a single aspect, either high sensitivity or wide bandwidth. Here, an adaptive robotic skin is proposed that has both high sensitivity and broad bandwidth with an augmented pressure sensing ability beyond the human skin. A key for the adaptive robotic skin is a tunable pressure sensor built with uniform gallium microgranules embedded in an elastomer, which provides large tuning of the sensitivity and the bandwidth, excellent sensor-to-sensor uniformity, and high reliability. Through the mode conversion based on the solid-liquid phase transition of gallium microgranules, the sensor provides 97% higher sensitivity (16.97 kPa-1 ) in the soft mode and 262.5% wider bandwidth (≈1.45MPa) in the rigid mode compared to the human skin. Successful demonstration of the adaptive robotic skin verifies its capabilities in sensing a wide spectrum of pressures ranging from subtle blood pulsation to body weight, suggesting broad use for various applications.