Blood Velocity Research Articles

Efficacy of a hands-free vascular ultrasound probe holder in active and inactive limbs during cycling exercise.

Measurement of blood flow during exercise is crucial for understanding physiological responses and performance outcomes. However, traditional methods are often invasive, costly, or require substantial training, limiting widespread research in this area. This study introduces the innovative use of limb-affixed ultrasound probe holders for vascular imaging during exercise to overcome these challenges. We investigated a commercially available probe holder, the Usono ProbeFix dynamic (PFD), in capturing artery diameter and blood velocity during dynamic exercise compared with a trained sonographer. Twenty healthy adults (11 females) underwent simultaneous imaging of the brachial artery and superficial femoral artery (SFA) using both manual and PFD imaging on separate days. Data were collected for 60 s at rest on a cycle ergometer and after 4 min of cycling at 50, 100, and 150 W. The PFD was comparable with a trained sonographer at rest (both 99 ± 2%) but demonstrated superiority in capturing blood velocity in the inactive limb (main effect of scanning condition P < 0.01; e.g., 150 W exercise: 85 ± 21% vs. 74 ± 25%). There was no effect of scanning condition on velocity capture success in the SFA (main effect: 69 ± 21% vs. 65 ± 16%; P = 0.42). A systematic constriction of brachial artery diameter (∼0.02 cm) was noted in the PFD condition (P < 0.01), likely due to the compression of the shallow artery. The findings suggest that ultrasound probe holders offer a promising solution for increasing accessibility to exercising blood flow in vascular physiology research, though require considerations for data cleaning and diameter assessment. Further investigation is warranted to optimize the application of these devices in dynamic exercise scenarios.NEW & NOTEWORTHY This study explores an ultrasound probe holder (PFD) for measuring blood flow during exercise, addressing the limitations of traditional methods. We compared PFD imaging with manual scanning in capturing artery diameter and blood velocity during cycling exercise. Results showed that the PFD matched trained sonographer accuracy at rest and outperformed them in capturing blood velocity during exercise in the inactive limb but not active limb. We highlight the PFD's potential impact in vascular physiology research.

Neuro-computational simulation of blood flow loaded with gold and maghemite nanoparticles inside an electromagnetic microchannel under rapid and unexpected change in pressure gradient.

In cardiovascular research, electromagnetic fields generated by Riga plates are utilized to study or manipulate blood flow dynamics, which is particularly crucial in developing treatments for conditions such as arterial plaque deposition and understanding blood behavior under varied flow conditions. This research predicts the flow patterns of blood enhanced with gold and maghemite nanoparticles (gold-maghemite/blood) in an electromagnetic microchannel influenced by Riga plates with a temperature gradient that decays exponentially, under sudden changes in pressure gradient. The flow modeling includes key physical influences like radiation heat emission and Darcy drag forces in porous media, with the flow mathematically represented through unsteady partial differential equations solved using the Laplace transform (LT) method. Results, including shear stress (SS) and rate of heat transfer (RHT), are graphically detailed, demonstrating changes in blood velocity profile with modifications in the Hartmann number and the width of electrodes, and differences in temperature and RHT between hybrid nano-blood (HNB) and nano-blood (NB). The key results indicate an increase in blood velocity distribution with higher modified Hartmann number, and a decrease with wider electrodes. Temperature is elevated in both hybrid nano-blood (HNB) and nano-blood (NB). Notably, HNB with gold and maghemite enhances heat transmission in the flow. Furthermore, an artificial intelligence-driven methodology employing an artificial neural network (ANN) has been incorporated to facilitate rapid and precise evaluations of SS and RHT, demonstrating remarkable predictive accuracy. The proposed algorithm exhibits outstanding accuracy, achieving 99.998% on the testing dataset and 96.843% during cross-validation for predicting SS, and 100% on the testing dataset, and 95.008% during cross-validation for predicting RHT. The implementation of nanotechnology with artificial intelligence promises new tools for doctors and surgeons, potentially transforming patient care in fields such as oncology, cardiology, and radiology. This model also facilitates the generation of precise electromagnetic fields to guide drug-loaded magnetic nanoparticles for applications in targeted drug delivery, hyperthermia treatment, MRI contrast enhancement, blood flow monitoring, cancer treatment, and controlled drug release.

Mathematical modeling of electroosmotic flow and thermal transport in stenotic tapered arteries using finite difference method

This study investigates the electroosmotic flow and thermal transport of nanofluids, specifically aluminum oxide and titanium dioxide, within tapered arteries with stenosis. Using the finite difference method (FDM), we modeled the flow dynamics and heat transfer mechanisms under the assumption of low Reynolds numbers and mild stenosis. The study focuses on the effects of nanoparticle volume fraction, heat absorption parameters, and electroosmotic forces on blood flow, velocity profiles, and temperature distribution. Results show that increasing nanoparticle concentration and heat absorption significantly reduce flow velocity, particularly in divergent artery geometries. Additionally, the inclusion of electroosmotic effects enhances heat transfer, while the Grashof number influences central velocity. These findings offer valuable insights into optimizing nanoparticle-based therapeutic interventions for cardiovascular treatments, providing a framework for enhancing drug delivery systems and improving the efficacy of heat-based therapies. The study’s outcomes could lead to improved diagnostic tools and therapeutic strategies for managing cardiovascular diseases.

Construction and validation of a prediction model for arteriovenous fistula thrombosis in patients with AVF using Lasso regression.

The primary objective of this study is to develop and validate a high-risk model for Arteriovenous Fistula Thrombosis (AVFT) in patients undergoing autogenous arteriovenous fistula surgery for hemodialysis. Retrospectively, we collected general information, clinical characteristics, laboratory examinations, and dialysis-related factors from a cohort of 1465 patients who received continuous arteriovenous fistula surgery at the Hemodialysis Access Center of Sichuan Provincial People's Hospital between January 2019 and June 2022. The patients were randomly divided into a training set and a validation set in a 2:1 ratio. The training set was utilized to select AVFT-related features using LASSO regression. A predictive model was constructed using logistic regression analysis, and its performance was assessed in the validation set. Through LASSO regression, we initially identified 13 candidate factors. Subsequently, based on the Akaike Information Criterion (AIC) principle, the following factors were selected to construct the AVFT prediction model: monocytes_ratio, Fistula blood velocity, cystatin-c, homocysteine, parathormone, artery_dysfunction, C-reactive protein, fibrinogen, and d-dimer. The discrimination C-index of the model in the training set was 0.8767. For this training set, the sensitivity was 48.05% and the specificity was 96.84%. In the validation set, the model's discrimination C-index, as evaluated by the ROC curve analysis, was 0.7888. The sensitivity was 14.29%, and the specificity was 97.04%. We assessed the calibration of the model using calibration curves, obtaining a maximum absolute difference of Emax = 0.205 and an average absolute difference of Eave = 0.032. Furthermore, we evaluated calibration and accuracy using the Spiegelhalter Z-test, yielding an S:P ratio of 0.704. AVFT is a multifactorial outcome influenced by factors such as injury, inflammatory factors, blood glucose levels, blood velocity, coagulation, electrolyte metabolism, and vascular endothelial function.

Two-fluid flow of blood in a curved stenotic artery under pulsating condition.

The present article focuses on the analysis of the two-phase flow of blood via a stenosed artery under the influence of a pulsatile pressure gradient. The core and plasma regions of flow are modeled using the constitutive relations of Herschel-Bulkley and the Newtonian fluids, respectively. The problem is modeled in a cylindrical coordinate system. A modest stenosis assumption is used to simplify the non-dimensional governing equations of the flow issue. An explicit finite difference approach is used to solve the resultant nonlinear system of differential equations while accounting for the provided boundary conditions. After the necessary adjustments have been made to the crucial non-dimensional parameters, an analysis of the data behind the huge image, such as axial velocity, temperature field, concentration wall shear stress, flow rate, and flow impedance, is conducted. The current study shows that the curvature of blood vessels plays a significant role in influencing blood velocity. Specifically, a unit increase in the curvature radius results in a 24% rise in blood velocity.

Effects of Continuous Graduated Pneumatic Compression and Intermittent Pneumatic Compression on Lower Limb Hemodynamics for VTE Prophylaxis in Arthroplasty.

Intermittent pneumatic compression (IPC) is considered the standard of care for preventing venous thromboembolism (VTE) in the hospital setting. However, its widespread adoption after hospitalization has been limited due to its shortcomings in obstruction of venous valves and blood reflux. The objective of this study is to compare the effects of continuous graduated pneumatic compression (CGPC), a new device with a novel mechanism, and IPC on lower hemodynamics and the incidence of VTE in patients undergoing arthroplasty. We randomized 123 participants undergoing knee arthroplasty to receive either IPC or CGPC from June 2022 through August 2023. An experienced sonographer used a Doppler ultrasound scanner to obtain hemodynamic indicators of venous blood. The primary outcome was the blood velocity of the femoral vein measured by a Doppler scanner. Secondary outcomes included the hemodynamic of the femoral vein and popliteal vein, quality of life at discharge and 30 days after surgery, symptomatic and asymptomatic VTE up to 30 days, and adverse events related to the IPC and CGPC device. For statistical analyses, Student's t-test, analysis of covariance, and the Mann-Whitney U test were used. Statistical significance was indicated with p < 0.05. There was no significant difference in femoral vein velocity between the IPC and CGPC groups. However, CGPC demonstrated a significant increase in femoral vein flow compared to the IPC group, with a median (interquartile) increasing from 158.9 (122.9, 204.3) to 265.6 (203.3, 326.8) mL/min in the CGPC group and from 139.0 (103.3, 175.9) to 189.6 (161.4, 270.8) mL/min in the IPC group (p < 0.001). Similar trends were observed in popliteal vein measurements. The differences between the two groups were similar in terms of quality of life, incidence of VTE, and adverse events. The CGPC device provides a substantial increase in blood flow compared to the IPC device. Its safety and effectiveness have been preliminarily validated. The CGPC device presents a promising alternative for VTE prophylaxis in arthroplasty. Chinese Clinical Trial Registry (registration number: ChiCTR2300078201).

Precision of in vivo pressure gradient estimations using synthetic aperture ultrasound.

Non-invasive estimation of pressure differences using 2D synthetic aperture ultrasound imaging offers a precise, low-cost, and risk-free diagnostic tool. Unlike invasive techniques, this preserves natural blood flow and avoids the limitations of devices that occupy lumen space. This paper evaluates a previously published estimator, modified to incorporate Singular Value Decomposition (SVD) echo-cancellation, using data from ten healthy volunteers and one patient. It is hypothesized that the estimator will enable precise pressure differences from the common carotid artery with a coefficient of variation of approximately 10% over a 10-second data acquisition period. Here, precision is essential to demonstrate the method's consistency and its ability to differentiate between healthy and diseased arteries at the earliest possible stage. Data are acquired using a GE-9L-D, 5.2 MHz linear transducer connected to a Vantage 256 research scanner. The estimator was applied to the left common carotid artery of ten healthy volunteers, with precision being evaluated over the recorded heart cycles by using the coefficient of variation. Eight out of ten individuals showed precision below 10%, whereas two individuals showed precision above 20%. The best precision was attained by subject_03 with a coefficient of variation of 4.64% (16.1 Pa) and the worst precision was attained by subject 09 with a coefficient of variation of 23.3% (30.2 Pa). The average range of pressure differences across volunteers (from maximum positive to maximum negative pressure difference) was 297 Pa when measured across a 14 mm streamline. The corresponding average coefficient of variation was found to be 9.95% (24.6 Pa). A comparison of peak systolic velocities between the experimental scanner and the reference scanner demonstrates a strong positive linear correlation (R2 = 0.76). The corresponding slope of the linear best fit is 0.95, indicating that the relationship between the two scanners is close to a one-to-one match, with the experimental scanner's measurements being slightly less than those of the reference scanner. Finally, data attained from a single patient example shows pressure differences ranging from -61.81 Pa to 1240.82 Pa with blood velocities as high as 1.73 m/s, which is significantly higher than seen in any of the healthy volunteers, supporting the likelihood of differentiating between stenosis grades in future studies. While this study is limited to 10 healthy volunteers and one patient, a different study design is needed to quantify the severity of stenosis and correlate it with pressure differences.

Cerebrovascular Compliance during Progressive Hypotension in Patients with Autonomic Failure.

The compliant nature of cerebral blood vessels may represent an important mechanical protection for sustained cerebral perfusion during reductions in arterial blood pressure (ABP). However, whether the rise in cerebrovascular compliance (Ci) with falling ABP persists and exhibits a threshold effect remains unknown. Therefore, we analyzed Ci changes during graded head-up tilt (HUT) in individuals with autonomic failure (AF), a group that tolerates graded and progressive reductions in ABP. Finger ABP and middle cerebral artery blood velocity (MCAv) were recorded from five AF patients (61 ± 22 years) at supine rest and during graded-HUT. Tilt gradients increased incrementally between 30, 45, and 60 degrees every 5 minutes until ABP reached a critically low value. The total time in HUT was 11 ± 4 min. Every 5 s during supine and HUT individual ABP and MCAv waveforms were assessed for Ci and cerebrovascular resistance (CVR) using a modified Windkessel model. Pulse pressure (PP) was calculated as systolic ABP - diastolic ABP. A threshold value for the increase in Ci was determined using breakpoint analysis of the linear relationship between changes in Ci and PP or ABP across tilt periods. Graded HUT resulted in reduced ABP, PP, CVR, and mean MCAv, and increased Ci (all P < 0.01). Ci began to increase progressively after PP fell by 22 ± 6 mmHg and ABP fell by 20 ± 11 mmHg. In conclusion, the increase in Ci during progressive hypotension exhibited a threshold effect and persisted as ABP continued to fall.

Effects of acetazolamide on intracranial pressure and brain tissue oxygenation on patients with acute brain injury: A pilot physiological study.

The effect of acetazolamide on regional brain tissue oxygenation in patients with acute brain injury (ABI) is unknown. We studied adult patients with ABI who received acetazolamide as per the treating physician's decision and had ICP and brain oxygen pressure (PbtO2) monitoring. Baseline measurements of ICP, cerebral perfusion pressure (CPP), and PbtO2 were taken before administering acetazolamide; subsequent measurements were recorded every 5 min for a total of 20 min. Mean cerebral blood velocities (FVm) and pulsatility index (PI) were measured using transcranial color-coded duplex (TCCD) sonography at baseline and after 20 min. Fourteen patients with subarachnoid hemorrhage (n = 6), traumatic brain injury (n = 7), and intracranial hemorrhage (n = 1) were included. Following administration of acetazolamide, ICP showed a significant increase within 20 min (p < 0.001), with no significant change in CPP (p = 0.08). PbtO2 demonstrated a significant increase (p < 0.001), with a noticeable change observed at 10 min after acetazolamide administration (15 [14-17] vs. 28 [26-30] mmHg). Additionally, FVm exhibited a significant increase (p < 0.001), and PI showed a reduction (p < 0.001). Administration of acetazolamide in ABI patients resulted in a significant increase in brain oxygenation, associated with a rise in ICP and FVm, suggesting increased cerebral volume and vasodilation.

Blood flow dynamics in the arterial and venous parts of the capillary.

Although there is currently sufficient information on various parameters of capillary blood flow, including the average values of blood velocity, there is no data on the dynamics of velocity and the mechanisms of its modulation in various parts of the capillary. The main idea of this work is to develop a tool and image data processing to study the characteristics of the capillary blood flow dynamics. In this study, using the developed method of high-speed videocapillaroscopy, the red blood cells (RBC) velocities in the arterial and venous parts of the nailfold capillaries were compared and a time-frequency analysis of the dynamics of the velocity signals with the calculation of phase coherence was performed. We indicated that the velocity in the arterial part is twice as high and that the ratio of velocities in the arterial and venous parts is stable regardless of the local velocity. This study also empirically confirms the similarity between the oscillations of blood flow in different parts of the capillary and the synchronization of the velocity phases. We believe that the determination of the absolute velocity characteristics of blood flow, together with the mechanisms of its regulation and the ratio of velocities in the arterial and venous parts, can act as a diagnostic approach.

Short- and long-term effects of transcutaneous spinal cord stimulation on autonomic cardiovascular control and arm-crank exercise capacity in individuals with a spinal cord injury (STIMEX-SCI): study protocol

IntroductionIndividuals with higher neurological levels of spinal cord injury (SCI) at or above the sixth thoracic segment (≥T6), exhibit impaired resting cardiovascular control and responses during upper-body exercise. Over time,...

FLUID FLOW AND THERMAL ANALYSIS OF BLOOD FLOW IN AN AUTOMATICALLY GENERATED 2D VASCULAR NETWORK FEATURING THE POROUS MEDIA-BASED OUTFLOW BOUNDARY CONDITIONS

Blood flow and thermal analyses in biological tissues are utterly important to better understand the transport phenomena in human tissues with reference to cardiovascular diseases, drug delivery, and thermal ablation. In the existing literature, there is room for new computationally lighter numerical analyses, including both fluid flow and heat transfer. This paper presents an analysis of blood thermo-fluid dynamics within an automatically generated two-dimensional (2D) vascular network, employing the constrained constructive optimization algorithm for structure generation, the porous media assumption for outflow boundary conditions, and heat transfer coefficient analysis for terminal vessels. Through comparisons with theoretical results, the model demonstrates mathematical robustness. Results of the simulations show that blood velocity decreases with increasing number of bifurcations, offering quantitative insights into its decay in magnitude and on its impact on heat transfer. Blood temperature rises in vessels with low velocity, hindering its cooling effects in the surrounding tissues. The study highlights the influence of bifurcation levels on heat transfer coefficient reduction, suggesting longer pathways and time periods to reach high temperature within the blood vessels, due to the cooling effect of pulsating blood flow in larger vessels. The quantitative analysis of the heat transfer coefficient and Nusselt number provides insights into heat transfer between blood and the surrounding tissue, offering also valuable information for numerical bioheat models in thermal therapy simulations.

Subcomponent analysis of the directional sensitivity of dynamic cerebral autoregulation.

The origin of the directional sensitivity (DS) of dynamic cerebral autoregulation (dCA) is not known. In 140 healthy participants (67 male, 27.5 ± 6.1 yr old), middle cerebral artery velocity (MCAv, transcranial Doppler), arterial blood pressure (ABP, Finometer), and end-tidal CO2 (EtCO2, capnography) were recorded at rest. Critical closing pressure (CrCP) and resistance-area product (RAP) were obtained for each cardiac cycle, as well as mean MCAv and ABP (MAP). The integrated positive and negative derivatives of MAP (MAP+D and MAP-D, respectively) were used as simultaneous inputs to an autoregressive moving average model to generate two distinct MCAv step responses. Similar models allowed the estimation of corresponding MAP-CrCP and MAP-RAP responses to step changes in MAP+D and MAP-D. The strength of DS (ΔDS) was expressed by the difference in mean values of the step responses for the time interval 12-18 s. ΔDS was significant for MCAv (8.5 ± 46.9% vs. 26.7 ± 42.0%, P < 0.001) and RAP (-93.9 ± 48.1 vs. -74.5 ± 43.0%, P < 0.001), respectively, for MAP+D and MAP-D inputs, but not for CrCP (2.2 ± 48.1% vs. 0.72 ± 42.9%, P = 0.76). Compared with males, female participants had higher MCAv (63.9 ± 15.6 cm/s vs. 55.4 ± 12.9 cm/s, P < 0.001) but lower EtCO2 (P < 0.001) and RAP (P = 0.015). Sex did not influence ΔDS for any of the three-step responses. The presence of directional sensitivity in the RAP, but not in the CrCP transfer function, suggests that the origin could be solely myogenic, without metabolic involvement.NEW & NOTEWORTHY The directional sensitivity of the cerebral blood velocity response to a sudden change in mean arterial blood pressure (MAP) is mediated by the resistance-area product, without involvement from the cerebral critical closing pressure. The reduced amplitude of MAP spontaneous fluctuations at rest suggests that it is less likely that directional sensitivity has origins in the sympathetic control of cerebral blood vessels, thus generating the need to consider other alternatives.

Larger reductions in blood pressure during post-exercise standing, but not middle cerebral artery blood velocity, in resistance-trained versus untrained individuals.

Dynamic resistance exercise (RE) produces sinusoidal fluctuations in blood pressure, with hypotension and cerebral hypoperfusion commonly observed immediately following RE. Whether the cerebral vasculature adapts to these regular blood pressure challenges is unclear. This study examined the cerebrovascular response to post-dynamic RE orthostasis. RE-trained (n=15, female=4) and healthy untrained individuals (n=15, female=12) completed five stands: one after seated rest, with each of the subsequent four stands occurring immediately following a set of 10 repetitions of unilateral leg extension exercise at 60% of their one repetition maximum. Beat-to-beat blood pressure, mean middle cerebral artery blood velocity (MCAvmean) and end-tidal carbon dioxide were measured throughout. During standing the mean arterial blood pressure (MAP) and MCAvmean nadirs were identified. There was no difference between groups for age (mean±SD, 26±7 RE-trained vs. 25±6years untrained, P=0.683) or weight (78±15 vs. 71±15kg, P=0.683). At MAP nadir during the post-exercise stand, a greater reduction in MAP was observed in the RE-trained group (e.g., set 4, -45±11 vs. -36±6mmHg, training effect P=0.026). However, post-exercise stand MCAvmean at MCAvmean nadir was not different (e.g., set 4, -20±7 vs. -17±6cm/s, interaction effect P=0.478). Rate of regulation was higher in the RE-trained group (set 1, 0.301±0.170 vs. 0.167±0.009, training effect P=0.023). Despite RE-trained individuals demonstrating greater absolute reductions in MAP during orthostasis following RE, there were no differences in MCAvmean, suggesting that habitual RE may mitigate post-exercise cerebral hypoperfusion.

Mathematical Fractional Analysis on Blood Casson Fluid in Slip and Small Arteries with the Cholesterol Porosity Effect

Studying human blood flow is crucial in biomedical research to address blood-related disorders. However, experimental studies are costly and time-consuming. Hence, mathematical models have been developed to represent these physical phenomena. Yet, existing models often overlook the slip boundary effect. This study explores an analytical solution for the pulsatile flow of a fractional Casson fluid in a slip cylinder, considering free convection, magnetic fields, and porosity. Employing the Caputo--Fabrizio fractional derivative method, the problem is modelled. Analytical solutions are obtained using Laplace and finite Hankel transforms. Graphical representations illustrate velocity and temperature profiles, emphasizing parameters such as magnetic, Casson, Darcy, fractional, slip, Grashof, and Prandtl numbers. Numerical results for skin friction and Nusselt number are tabulated. The results suggest that enhanced slip velocity amplifies fluid flow, particularly near the cylinder's surface, generating lubrication to alleviate blood-vessel friction and improve blood flow by enabling smoother movement along vessel walls. The fractional-order derivative fluid model is more practical and realistic compared to the classical fluid model due to its memory effect which sudden rise in blood velocity can potentially damage the blood vessel and lead to atherosclerosis. The obtained analytical result can be used to validate the accuracy of the mathematical model obtained by numerical methods.

The role of sympathetic control in bone vasculature: insights from spinal cord injury.

Bone vasculature is richly innervated by an extensive network of sympathetic nerves. However, our understanding of bone blood flow regulation and its contribution to human bone health is limited. Here, we further our previous findings by characterizing bone vascular responses in the absence of sympathetic control - studying individuals with spinal cord injury (SCI), a population with known peripheral sympathetic disruption. We assessed tibial vascular responses to isometric handgrip exercise (IHE) in individuals with SCI (n = 12) and controls (n = 12). When sustained to fatigue, IHE increases perfusion pressure and sympathetic vasoconstriction in the non-active tissues of the legs. During IHE, we measured blood pressure, whole leg blood velocity via ultrasound, and tibial perfusion (as hemoglobin content) via near-infrared spectroscopy. Controls demonstrated active sympathetic vasoconstriction in the whole leg (i.e., increased vascular resistance, arterial pressure/leg blood velocity) and tibia (i.e., decreased hemoglobin). In contrast, SCI individuals demonstrated modest whole leg vasoconstriction with lesser increases in vascular resistance than controls (P<.04). Tibial vasculature evidenced absent or blunted vasoconstriction compared to controls (P<.01), indicated by increasing tibial hemoglobin until plateauing at higher pressure levels. This suggests that, in the absence of sympathetic control, tibial vascular response may involve other regulatory mechanisms like myogenic vasoconstriction. Lastly, we leveraged existent whole-body Dual Energy X-ray Absorptiometry scans in a subgroup of nine individuals with SCI and we found a strong relationship between leg bone mineral density (BMD) and tibial hemoglobin at end of IHE (r2 = 0.67, P<.01). Our findings indicate that in the absence of sympathetic mechanisms, myogenic control may play a compensatory role in regulating blood flow, though to a lesser extent in bone compared to muscle. The close relationship between lesser declines in bone blood content and higher BMD underscores the link between blood flow and bone health.

A prospective study of the effect of laparoscopic splenectomy and azygoportal disconnection on liver synthetic function and liver cirrhosis

Objective: To investigate the effect of laparoscopic splenectomy and azygoportal disconnection (LSD) on liver synthesis and development of liver cirrhosis. Methods: This is a prospective case series study.The clinical data of liver cirrhotic patients with portal hypertension who received LSD at the Department of Hepatobiliary Surgery of Northern Jiangsu People's Hospital Affiliated to Yangzhou University from September 2014 to January 2016 were included. This study analyzed the diameter of the portal vein, the velocity of portal blood flow, the routine blood parameters, the liver function, the synthetic proteins of liver (antithrombin Ⅲ (AT-Ⅲ), protein S, protein C), and the serum content of liver fibrotic markers(collagen type Ⅳ, procollagen type Ⅲ, laminin, hyaluronidase). Repeated measures ANOVA was used for comparison between multiple groups, and least significance difference was used for post-hoc multiple comparison. Results: A total of 106 patients were included in the study, including 70 males and 36 females, aged (51.8±9.8) years(range: 28 to 75 years).Compared with the preoperative results, the diameter of portal vein and the velocity of portal vein decreased after surgery (F=14.03, 12.15, respectively, both P<0.01). Compared with the preoperative results, the total bilirubin, albumin, prothrombin time, international normalized ratio, Child-Pugh score and classification were improved (F=17.96, 56.01, 66.63, 35.83, 33.49, and 27.50, respectively, all P<0.01), and the AT-Ⅲ, protein S, protein C,collagen type Ⅳ, procollagen type Ⅲ, laminin and hyaluronidase levels were also improved (F=47.87, 36.26, 18.02, 2.79, 14.58, 44.35, and 14.38, respectively, all P<0.01). Compared with the preoperative period, the diameter of portal vein was reduced from the first week to the 24th month after surgery (t=5.45 to 9.39, all P<0.01). Compared with the preoperative period, the velocity of portal vein blood from the first week after surgery to the 24th month after surgery was decreased (t=4.02 to 8.43, all P<0.01). Compared with the preoperative period, routine blood parameters (white blood count, hemoglobin, platelet count), liver function (total bilirubin, albumin, prothrombin time, international normalized ratio, Child-Pugh score), liver synthetic protein (AT-Ⅲ, protein S, protein C) and liver fibrotic markers (collagen type Ⅳ, procollagen type Ⅲ, laminin, hyaluronidase) were improved to varying degrees at the 24th month after surgery (t=-20.46 to 11.93, all P<0.01). Conclusion: Preliminary findings show that LSD can reduce portal vein pressure, restore blood cell number, and improve liver synthesis function and the degree of liver fibrosis in patients with portal hypertension in liver cirrhosis.

The Influence of Sex, Fitness, BMI, and Cardiovascular Risk Factors on Cerebral Blood Velocity Responsiveness to Graded Exercise Testing in Middle-Aged Adults.

Mean middle cerebral artery velocity (MCAv) and the pulsatility index (PI), at rest and in response to exercise, are important markers of cerebrovascular health status in middle-aged adults, when vascular decline assumes substantial relevance. Thus, this study aimed to describe and compare the responses of MCAv and PI to incremental exercise. Two hundred and forty-eight volunteers (50-58 years, 55% women) completed a ramp test on a cycle-ergometer. Gas exchange was assessed on a breath-by-breath basis. MCAv was measured via transcranial Doppler and PI calculated. Cardiovascular disease risk (CVR) factors were determined and comprised of measurements of central obesity, blood pressure, fasted plasma glucose, and lipids. The MCAv and PI responses to exercise were compared across body mass index categories, CVR score, and fitness status. We found sex-specific differences in MCAv and PI at rest. However, both sexes showed a similar relative change to baseline (Δ%MCAvmean). Regarding body mass index, obese women (body mass index > 30 kg m-2) had lower MCAv and Δ%MCAvmean and higher PI compared with normo-weight women during exercise. Apart, women with a 0 CVR score showed higher MCAv and lower PI during exercise than those with a score of +3 CVR. Differences between low and high CVR during exercise in Δ%MCAvmean were also found. Eventually, low fitness showed diminished MCAv and a lower response to exercise than high fitness. This study has highlighted significant variability in MCAv responsiveness to exercise among middle-aged adults. Body composition, CVR, and fitness status may play a significant role in preserving cerebrovascular health. These findings shed light on the importance of understanding the cerebrovascular response to exercise.

Sex differences between postmenopausal women and similar-age men in response to orthostatic stress following 2 wk of bed rest.

Reduced orthostatic tolerance is common following periods of bed rest that are associated with illness or surgery, putting individuals at higher risk for syncope and falls following hospitalization. Following menopause, mechanisms of female cardiovascular regulation change, which may be associated with sex-specific responses to orthostatic stress following bed rest. The purpose of our experiment was to investigate sex differences between healthy postmenopausal women and similar-age men (age: 55-65 yr) for their orthostatic tolerance and cerebrovascular responses to standing following bed rest. Twenty-two late-middle-aged adults (11 women) completed 14 days of head-down bed rest, with half of the participants being randomized into an exercise group that performed high-intensity exercise during bed rest. Supine-to-stand tests were performed before and ∼5 h after bed rest. Women had lower orthostatic tolerance than men after bed rest (bed rest × sex interaction: P = 0.004), without a protective effect of daily exercise. Both men and women were mildly hypocapnic while supine (main effect: P = 0.019) following bed rest and had lower middle cerebral artery blood velocity (MCAv) nadirs upon standing (main effect: P = 0.027). During the third minute of standing, both men and women had lower end-tidal Pco2 (main effect: P < 0.001) and MCAv (main effect: P = 0.002) after bed rest, but only men had increased cerebrovascular resistance index (bed rest × sex interaction: P = 0.005) and only women were hypotensive (bed rest × sex interaction: P = 0.020) compared with pre-bed rest. Accordingly, lower MCAv of postmenopausal women and men while standing after bed rest was mediated by different factors.NEW & NOTEWORTHY Postmenopausal women had lower orthostatic tolerance than similar-age men while standing post-bed rest. Both sexes exhibited lower cerebral blood velocity nadirs upon standing; however, sex-specific interactions of the determinants of cerebral perfusion (i.e., Pco2, cerebrovascular resistance index, and arterial pressure) were observed during prolonged standing after bed rest. These results indicate that postmenopausal women and men have different factors underlying reduced cerebral perfusion while standing after bed rest.

Lower neurovascular coupling response despite higher cerebral blood flow at rest in apolipoprotein ɛ4 positive adults.

Cerebral blood flow at rest declines with age. However, age-related changes in functional measures of cerebrovascular health including cerebrovascular reactivity and neurovascular coupling are not well understood. Additionally, the effect of apolipoprotein E (APOE) ε4, a strong genetic risk factor for Alzheimer's disease, on cerebral blood flow and cerebrovascular function remains unclear. APOEε4 positive (APOEε4+; n = 37, age = 63±4y) and APOEε4 negative (APOEε4-; n = 50, age = 63±4y) cognitively unimpaired adults participated in this study. Macrovascular cerebral blood flow and microvascular cerebral perfusion were measured using 4D flow MRI and pseudo-continuous arterial spin labeling MRI, respectively. Cerebrovascular reactivity and neurovascular coupling were assessed by measuring middle cerebral artery blood velocity in response to hypercapnia and the n-back test, respectively. Neurovascular coupling was lower in APOEε4+ compared with APOEε4- adults (P<0.05), despite higher cerebral blood flow and cerebrovascular reactivity to hypercapnia. Alterations in neurovascular coupling may occur early, prior to changes in cognition, in aging APOEε4 carriers.