Jugular Venous Flow Quantification Using Doppler Sonography

Exposure to a weightless environment during spaceflight results in a chronic headward blood and tissue fluid shift compared with the upright posture on Earth, with unknown consequences to cerebral venous outflow. To assess internal jugular vein (IJV) flow and morphology during spaceflight and to investigate if lower body negative pressure is associated with reversing the headward fluid shift experienced during spaceflight. This prospective cohort study included 11 International Space Station crew members participating in long-duration spaceflight missions . Internal jugular vein measurements from before launch and approximately 40 days after landing were acquired in 3 positions: seated, supine, and 15° head-down tilt. In-flight IJV measurements were acquired at approximately 50 days and 150 days into spaceflight during normal spaceflight conditions as well as during use of lower body negative pressure. Data were analyzed in June 2019. Posture changes on Earth, spaceflight, and lower body negative pressure. Ultrasonographic assessments of IJV cross-sectional area, pressure, blood flow, and thrombus formation. The 11 healthy crew members included in the study (mean [SD] age, 46.9 [6.3] years, 9 [82%] men) spent a mean (SD) of 210 (76) days in space. Mean IJV area increased from 9.8 (95% CI, -1.2 to 20.7) mm2 in the preflight seated position to 70.3 (95% CI, 59.3-81.2) mm2 during spaceflight (P < .001). Mean IJV pressure increased from the preflight seated position measurement of 5.1 (95% CI, 2.5-7.8) mm Hg to 21.1 (95% CI, 18.5-23.7) mm Hg during spaceflight (P < .001). Furthermore, stagnant or reverse flow in the IJV was observed in 6 crew members (55%) on approximate flight day 50. Notably, 1 crew member was found to have an occlusive IJV thrombus, and a potential partial IJV thrombus was identified in another crew member retrospectively. Lower body negative pressure was associated with improved blood flow in 10 of 17 sessions (59%) during spaceflight. This cohort study found stagnant and retrograde blood flow associated with spaceflight in the IJVs of astronauts and IJV thrombosis in at least 1 astronaut, a newly discovered risk associated with spaceflight. Lower body negative pressure may be a promising countermeasure to enhance venous blood flow in the upper body during spaceflight.

Clinical Applicability of Assessment of Jugular Flow over the Individual Cardiac Cycle Compared with Current Ultrasound Methodology

Umbilical venous blood flow could be considered a direct and physiological measurement of vascular placental function, representing the quantity of oxygen and nutrients reaching the fetus. The advent of high-technology ultrasound and pulsed Doppler has overcome some of the limitations of early studies. Indeed, Doppler measurement of umbilical venous blood flow has been found to be accurate when compared with several gold standards for in-vivo flow calculation. Nevertheless, small errors in volume flow components, the vessel area and the mean velocity, result in large errors in the calculation of volume flow. Therefore, technique standardization is of paramount importance. Validation studies in animal models have demonstrated accurate venous blood flow measurements by estimating the vessel's cross-sectional area from perpendicular views of longitudinal sections of free-floating portions of the cord. On the other hand, estimation of the mean velocity from the maximum velocity, rather than using the intensity-weighted mean velocity, is less software-dependent and more clearly defined, yielding estimates with more predictable and systematic errors. By adhering to stringent methodological recommendations, umbilical venous blood flow calculation has moderate to good intra- and interobserver reproducibility. Having been found to be accurate and reproducible, further studies are required to establish the clinical value of umbilical vein flow measurement.

The impact of orthostatic challenge on arteriovenous hemodynamics and volume changes of the lower extremity.

PurposeIn vivo measurements of CSF and venous flow using real-time phase-contrast (RT-PC) MRI facilitate new insights into the dynamics and physiology of both fluid systems. In clinical practice, however, use of RT-PC MRI is still limited. Because many forms of hydrocephalus manifest in infancy and childhood, it is a prerequisite to investigate normal flow parameters during this period to assess pathologies of CSF circulation. This study aims to establish reference values of CSF and venous flow in healthy subjects using RT-PC MRI and to determine their age dependency.MethodsRT-PC MRI was performed in 44 healthy volunteers (20 females, age 5–40 years). CSF flow was quantified at the aqueduct (Aqd), cervical (C3) and lumbar (L3) spinal levels. Venous flow measurements comprised epidural veins, internal jugular veins and inferior vena cava. Parameters analyzed were peak velocity, net flow, pulsatility, and area of region of interest (ROI). Statistical tests: linear regression, student's t-test and analysis of variance (ANOVA).ResultsIn adults volunteers, no significant changes in flow parameters were observed. In contrast, pediatric subjects exhibited a significant age-dependent decrease of CSF net flow and pulsatility in Aqd, C3 and L3. Several venous flow parameters decreased significantly over age at C3 and changed more variably at L3.ConclusionFlow parameters varies depending on anatomical location and age. We established changes of brain and spinal fluid dynamics over an age range from 5–40 years. The application of RT-PC MRI in clinical care may improve our understanding of CSF flow pathology in individual patients.

BackgroundDuring pregnancy, a number of changes affecting venous blood flow occur in the circulatory system, such as reduced vein wall tension or increased exposure to collagen fibers. These factors may cause blood stagnation, swelling of the legs, or endothelial damage and consequently lead to development of venous disease.ObjectivesThe aim of this study is to evaluate the effect of special footwear designed to improve blood circulation in the feet on venous blood flow changes observed during advancing phases of pregnancy.MethodsThirty healthy pregnant women participated in this study at 25, 30, and 35 weeks of gestation. Participants were allocated at random to an experimental group (n = 15) which was provided with the special footwear, or a control group (n = 15). At each data collection session, Doppler measurements of peak systolic blood flow velocity and cross-sectional area of the right popliteal vein were performed using a MySonoU6 ultrasound machine with a linear transducer (Samsung Medison). The differences were compared using Cohen’s d test to calculate effect size.ResultsWith advancing phases of pregnancy, peak systolic velocity in the popliteal vein decreased significantly in the control group, whereas it increased significantly in the experimental group. No significant change in cross-sectional area was observed in any of the groups.ConclusionsFindings in the experimental group demonstrated that wearing the footwear tested may prevent venous blood velocity from reducing during advanced phases of pregnancy. Nevertheless, there is a need for further investigation of the beneficial effect on venous flow of the footwear tested and its application.

The purpose of our study was to assess flow characteristics of vessels in the ligamentum teres fissure with color Doppler sonography in subjects without and with portal hypertension. Color Doppler sonography of the ligamentum teres fissure was performed with either a 5.0- or a 7.5-MHz linear transducer in 55 consecutive thin healthy volunteers. Retrospective review was performed of sonograms of 21 consecutive patients with portal hypertension in whom blood flow in a paraumbilical vein was shown with 2.0- to 5.0-MHz sector/curved array transducers. Nine (16%) of the 55 healthy subjects had venous flow in the ligamentum teres fissure, which was hepatofugal in five and hepatopetal in four. Hepatofugal venous flow velocity in the ligamentum teres fissure did not exceed 5 cm/sec (mean, 3.2 cm/sec; SD, 1.0 cm/sec; range, 2-5 cm/sec), and flow extending anterior to the liver's surface was not noted with color Doppler sonography in the healthy subjects. In the 21 patients with portal hypertension, venous flow in the ligamentum teres fissure was always 7 cm/sec or greater (mean, 16 cm/sec; SD, 7.1 cm/sec; range, 7-33 cm/sec) and was shown by color Doppler sonography to continue beyond the anterior surface of the liver in 12 patients (57%). Slow (< or = 5 cm/sec) hepatofugal venous blood flow may be detected in the ligamentum teres fissure in healthy subjects and by itself does not necessarily indicate portal hypertension. Hepatofugal venous flow in the ligamentum teres fissure with a velocity greater than 5 cm/sec or visualized with color Doppler sonography continuing anterior to the liver's surface is highly specific (100% in this series) for the presence of portal hypertension.

Blood flow through the anterior interventricular vein was measured in 17 dogs under normal conditions and after ligating the descending artery. In 10 of these dogs retrograde blood flow was measured in the peripheral stump of the descending ramus and in the anterior interventricular vein 10 and 11 min later. After ligating the descending ramus 16.6–70.5% blood flowed through the ischaemic area into the anterior interventricular vein. The origin of the blood is two-fold: (a) arterial – blood reaching the ischaemic area via arterio-arterial anastomoses and the capillary bed into the vein; (b) venous – from veins of the nonischaemic area via venous anastomoses into veins of the ischaemic area. This flow was explained on a morphological basis by veno-venous anastomoses and by finding a venous pressure gradient between the ischaemic and nonischaemic area. In most cases (in 8 dogs), venous flow from the infarcted area was 14–91 % greater (average 47%) than retrograde flow in the peripheral stump of the artery. In two dogs only was venous blood flow the same or less than arterial. In casts of these two hearts, unlike the previous cases, the supply area of the descending artery and the drainage area of the anterior interventricular vein did not coincide and blood was partly drained into veins of the nonischaemic part. The results show that some of the blood flowing through the ischaemic focus is inadequate for the myocardium on account of its place of origin and consequent lack of oxygen. The possibility of influencing the retrograde arterial blood flow by ligating the septal artery or not is dealt with in the discussion.

Below-knee cast immobilization is associated with an increased risk of developing deep vein thrombosis secondary to venous stasis. We investigated the effect of weight-bearing in a below-knee cast or pneumatic walking boot on lower limb venous blood flow. Duplex ultrasonography was used to measure venous blood flow in the popliteal vein of 10 healthy volunteers. Venous blood flow was measured while at rest, ambulating non-weight-bearing, partial weight-bearing, and full weight-bearing. Measurements were performed without ankle joint immobilization, with the ankle immobilized in a neutral cast, and with the ankle immobilized in a pneumatic walking boot in both neutral and equinus. There was no significant reduction in venous blood flow measurements between full weight-bearing without ankle joint immobilization and full weight-bearing in a neutral cast or neutral pneumatic walking boot. However, venous blood flow was reduced when partial weight-bearing (50%) and when full weight-bearing in a pneumatic walking boot in equinus. These results demonstrate that venous blood flow returned to normal levels when the subjects were permitted to fully bear weight in below-knee casts or walking boots, provided that the ankle joint was not in equinus. Weight-bearing status and ankle joint position should be appreciated during decisions for the provision of chemical thromboprophylaxis.

The vascular system regulates brain clearance through arterial blood flow and lymphatic drainage of cerebrospinal fluid (CSF). Idiopathic intracranial hypertension (IIH), characterized by elevated intracranial pressure and dural venous sinus stenoses, can be treated by restoring venous blood flow via venous stenting, suggesting a role for venous blood flow in brain fluid clearance. Using magnetic resonance imaging (MRI) in IIH patients and healthy controls, we identified that dural venous stenoses in IIH were associated with impaired lymphatic drainage, perivenous fluid retention, and brain fluid accumulation. To investigate this further, we developed a mouse model with bilateral jugular vein ligation (JVL), which recapitulated key human findings, including intracranial hypertension, calvarial lymphatic regression, and brain swelling due to impaired clearance. To further dissect the respective roles of meningeal lymphatic vessels and venous blood flow in brain clearance, we performed JVL in mice with lymphatic depletion. These mice exhibited spontaneous elevated intracranial pressure, but JVL did not further exacerbate this effect. Moreover, the synchronous restoration of brain clearance and meningeal lymphatics observed in mice after JVL was absent in lymphatic-deficient mice.Transcriptomic analyses revealed that lymphatic remodeling induced by JVL was driven by VEGF-C signaling between dural mesenchymal and lymphatic endothelial cells. These findings establish the dural venous sinuses as a critical platform where venous blood flow interacts with mesenchymal cells to preserve meningeal lymphatic integrity and function, essential for brain fluid clearance.

Accuracy of dilution techniques for access flow measurement during hemodialysis

Conservative therapy of adnexal torsion employing color doppler sonography

(1) Hepatic and portal venous blood flows were measured by a electromagnetic flowmeter in dogs for studying the effects of epinephrine and nor-epinephrine and of the greater splanchnic nerve stimulation on the hepatic and portal circulation.(2) Epinephrine and nor-epinephrine administered into the portal vein or hepatic artery caused a decrease in hepatic venous blood flow in spite of a slight increase in arterial pressure, indicating that these catecholamines had vasoconstrictor effects on the hepatic circulation. It was shown that the effects were somewhat greater when they were administered into the hepatic artery than when administered into the portal vein.(3) Administration of epinephrine or nor-epinephrine into the femoral or portal vein caused a decrease in portal venous blood flow associated with an increase in mesenteric vascular resistance (MR) and portal venous vascular resistance of hepatic side (HR). Administration into the femoral vein was followed by a more marked increased of MR than that of HR, however, administration into the portal vein caused a more marked increase of HR than that of MR. These observations suggested that the mechanisms of the decrease in portal venous blood flow by epinephrine and norepinephrine were different according to the route of their administration.(4) The greater splanchnic nerve stimulation caused an arterial pressure rise of diphasic pattern. The first peak of arterial pressure was consistently accompanied by an increase of hepatic venous blood flow and pressure, and the second peak was accompanied by a decrease of hepatic venous blood flow and pressure.(5) By the stimulation of the greater splanchnic nerve portal venous blood flow was increased initially in some cases and decreased subsequently in accordance with the second peak of arterial pressure in all cases. MR and HR were markedly increased with the decrease of portal venous flow, and the changes in MR were greater than those in HR. Therefore, the mechanism of the decrease in portal venous blood flow induced by the stimulation of the greater splanchnic nerve is considered to be reflected by the changes in the mesenteric blood vessels and to be similar to that induced by the administration of epinephrine or nor-epinephrine into the femoral vein.

To evaluate changes in liver perfusion after occlusion of spontaneous portosystemic shunt and to analyze mechanisms of liver profile improvement. Liver function changes and portal venous and hepatic arterial blood flow were evaluated using perfusion CT before and after shunt occlusion in 23 patients who underwent percutaneous occlusion of spontaneous portosystemic shunt because of gastric varices (n=15) or hepatic encephalopathy (n=8). Portal venous blood flow was significantly higher at 1week (278.7ml/min, 92.7-636.7, p=0.012), 1month (290.0ml/min, 110.1-560.1, p<0.001) and 3months (299.6ml/min, 156.7-618.5, p=0.033) after shunt occlusion than the baseline (220.9ml/min, 49.5-566.7). Hepatic arterial liver blood flow became lower than the baseline (132.3ml/min, 47.9-622.3) after shunt occlusion, but a significant decrease was observed only at 1month later (107.9ml/min, 45.8-263.6 p=0.027). Serum albumin concentration became significantly higher than the baseline (3.4mg/dl, 1.9-4.5) at 1month (3.8mg/dl, 2.3-4.3, p=0.018) and 3months (3.9mg/dl, 2.6-4.3, p=0.024) after shunt occlusion. Shunt occlusion increases portal venous blood flow and decreases hepatic arterial blood flow, thereby improving the liver profile.

We have studied the relationship between movements of the foot and ankle and venous blood flow from the lower limb using colourflow Duplex ultrasound to determine the optimum type of exercise for promoting venous return. Studies of both active and passive movements were carried out on 40 limbs in 20 subjects (18 men; 2 women), with a median age of 27 years (20 to 54). We assessed ankle dorsiflexion and plantar flexion, subtalar inversion and eversion, and a combination of all movements. There was no difference in venous flow when comparing opposite limbs in a single subject (p > 0.5), but active exercises produced higher peak and mean velocities of blood flow than passive ones. The active combined movement produced the highest velocities with an increase of 38% in mean and of 58% in peak flow velocities, which were significantly greater than the peak and mean flow rates produced by passive movements. The active combined exercise would therefore be the most effective in eliminating stasis and could contribute to the prevention of deep-vein thrombosis.