Measurement Of Arterial Blood Flow Research Articles

Features of changes in the heart, blood vessels and internal organs in men with hypertension, depending on the value of the body mass index

Objective: study of the features of changes in the heart, blood vessels and internal organs (liver and kidneys) in men with hypertension, depending on the BMI value. Materials and methods: 194 men aged 25 to 63 with hypertension were examined. All the examined patients were divided into 3 groups depending on the BMI value. All patients included in the study were determined by serum creatinine (calculated by GFR), glucose, aspartate aminotransferase, alanine aminotransferase, lipid spectrum, uric acid. In addition, echocardiography, ultrasound of the kidneys with measurement of arterial and venous blood flow through the main vessels of the kidneys, ultrasound of the liver were performed. In the future, the groups were compared with each other according to the studied laboratory and instrumental data. Results: as the BMI values increased, the indicators of alanylaminotransferase, IFDS, RWT LV, MMLV, IMLV, the size of the right lobe of the liver, the incidence of hepatosteatosis significantly increased. Adherence to antihypertensive therapy in the selected groups ranged from 18,9 to 20,5%. Bilateral disorders of outflow through the renal veins were 1,8 times more common among people with normal BMI compared with obesity (p<0.05). Conclusion: among the examined young men with hypertension, there are features of an unfavorable "cardiological" profile and low adherence to antihypertensive therapy, which, as the age and length of the disease increases, is associated with a high risk of developing associated clinical conditions in the future. In male patients with hypertension and obesity, the incidence of hepatosteatosis is 100%, having an additional adverse effect on cardiovascular risk. The revealed features of renal venous blood flow among patients with hypertension deserve further investigation.

High-speed measurement of retinal arterial blood flow in the living human eye with adaptive optics ophthalmoscopy.

We present a technique to measure the rapid blood velocity in large retinal vessels with high spatiotemporal resolution. Red blood cell motion traces in the vessels were non-invasively imaged using an adaptive optics near-confocal scanning ophthalmoscope at a frame rate of 200 fps. We developed software to measure blood velocity automatically. We demonstrated the ability to measure the spatiotemporal profiles of the pulsatile blood flow with a maximum velocity of 95-156 mm/s in retinal arterioles with a diameter >100 µm. High-speed and high-resolution imaging increased the dynamic range, enhanced sensitivity, and improved the accuracy when studying retinal hemodynamics.

GLP-1 Promotes Cortical and Medullary Perfusion in the Human Kidney and Maintains Renal Oxygenation During NaCl Loading.

Background GLP-1 (glucagon-like peptide-1) receptor agonists exert beneficial long-term effects on cardiovascular and renal outcomes. In humans, the natriuretic effect of GLP-1 depends on GLP-1 receptor interaction, is accompanied by suppression of angiotensin II, and is independent of changes in renal plasma flow. In rodents, angiotensin II constricts vasa recta and lowers medullary perfusion. The current randomized, controlled, crossover study was designed to test the hypothesis that GLP-1 increases renal medullary perfusion in healthy humans. Methods and Results Healthy male participants (n=10, aged 27±4 years) ingested a fixed sodium intake for 4 days and were examined twice during a 1-hour infusion of either GLP-1 (1.5 pmol/kg per minute) or placebo together with infusion of 0.9% NaCl (750 mL/h). Interleaved measurements of renal arterial blood flow, oxygenation (R2*), and perfusion were acquired in the renal cortex and medulla during infusions, using magnetic resonance imaging. GLP-1 infusion increased medullary perfusion (32±7%, P<0.001) and cortical perfusion (13±4%, P<0.001) compared with placebo. Here, NaCl infusion decreased medullary perfusion (-5±2%, P=0.007), whereas cortical perfusion remained unchanged. R2* values increased by 3±2% (P=0.025) in the medulla and 4±1% (P=0.008) in the cortex during placebo, indicative of decreased oxygenation, but remained unchanged during GLP-1. Blood flow in the renal artery was not altered significantly by either intervention. Conclusions GLP-1 increases predominantly medullary but also cortical perfusion in the healthy human kidney and maintains renal oxygenation during NaCl loading. In perspective, suppression of angiotensin II by GLP-1 may account for the increase in regional perfusion. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT04337268.

The Value of Non-invasive Electrocardiography in Assessing Fetal Status at Term Delivery.

The electrocardiograph (ECG) is efficient method for the accurate assessment of fetal heart rate. The barriers for accurate assessment are maternal heart rate, uterine contractions and abdominal muscles. Although previous monitoring methods have struggled to overcome these barriers, recent advances have led to a greater degree of success for listening and recording pulse-by-pulse fetal heart rate. A prospective cohort study evaluating the use, reliability and safety of non-invasive electrocardiography, in conjunction with Fetal Heart Rate parameters such as, Short Term Variability (STV) together with umbilical cord PH and Apgar score, during the active phase of childbirth. A total of 41 women with single, normal, full-term pregnancies had systematic obstetric monitoring with Monica AN24. 20 had only monitoring and 21 also had and arterial blood flow measurements. pH was measured and correlated with neonatal Apgar score at 1 and 5 min. The study also included a questionnaire about the safety and usability of obstetric monitoring. Statistical analysis was done using IBM SPSS v. 26.0. Mean age was 28.8 years, (SD ± 6.153). Electrocardiogram recordings (ECG) were classified as normal (71%) and suspicious (29%). Baseline between ECGs was different (p = 0.025) similarly for Short term variability (STV) (p <0.0001). BMI did not differentiate SVT rates. Only high acceleration (p <0.029) and small slowdowns had a statistically significant difference between normal and suspected cardiographs (p <0.029). APGAR score did not differ, whereas the umbilical cord pH was different in normal ECGs compared to the suspect (p = 0.012) and STV was also differentiated. A usability and safety survey was conducted after recording with MONIKA AN24, and the response to whether they would accept recording with the device again, was positive for 96% of the 30 responders. The present study shows that the use of electrocardiography in obstetrics allows to draw conclusions about the fetal hematopoiesis and oxygenation status. This method could be clinically applied and be an important tool for further screening in embryos that may be hypoxic and to decide whether to continue with a vaginal or cesarean delivery, thereby achieving the goal of reducing perinatal morbidity and mortality.

Repeatability assessment for simultaneous measurement of arterial blood flow, venous oxygen saturation, and muscle perfusion following dynamic exercise.

The purpose of the present study was to demonstrate a new sequence and determine the repeatability of simultaneous dynamic measurements of blood flow, venous oxygen saturation (SvO2 ), and relative perfusion (change from resting perfusion) in calf muscle during recovery from plantar flexion exercise. The feasibility of near simultaneous measurement of bio-energetic parameters was also demonstrated. A sequence was developed to simultaneously measure arterial blood flow using flow-encoded projection, SvO2 using susceptibility-based oximetry, and relative perfusion using arterial spin labeling in combination with dynamic plantar flexion exercise. The parameters were determined at rest and during recovery from single leg plantar flexion exercise. Test-retest repeatability was analyzed using Bland-Altman analysis and intraclass correlation coefficients (ICC). The mitochondrial capacity of skeletal muscle was also measured immediately afterwards with dynamic phosphorus magnetic resonance spectroscopy. Eight healthy subjects participated in the study for test-retest repeatability. Popliteal artery blood flow at rest was 1.79 ± 0.58 ml/s and increased to 11.18 ± 3.02 ml/s immediately after exercise. Popliteal vein SvO2 decreased to 45.93% ± 6.5% from a resting value of 70.46% ± 4.76% following exercise. Relative perfusion (change from rest value) was 51.83 ± 15.00 ml/100 g/min at the cessation of exercise. The recovery of blood flow and SvO2 was modeled as a single exponential with time constants of 38.03 ± 6.91 and 71.19 ± 14.53 s, respectively. All the measured parameters exhibited good repeatability with ICC ranging from 0.8 to 0.95. Bioenergetics measurements were within normal range, demonstrating the feasibility of near simultaneous measurement of hemodynamic and energetic parameters. Clinical feasibility was assessed with Barth syndrome patients, demonstrating reduced oxygen extraction from the blood and reduced mitochondrial oxidative capacity compared with healthy controls. The proposed protocol allows rapid imaging of multiple parameters in skeletal muscle that might be affected in disease.

Quantifying the Cardiovascular Physiology of REBOA and Partial REBOA: How REBOA Facilitates Resuscitation but Also Strains the Left Ventricle

Resuscitative endovascular balloon occlusion of the aorta (REBOA) is increasingly used as an endovascular approach to aortic occlusion. This can provide complete or partial aortic occlusion and is thereby known to augment afterload relative to the extent of occlusion. Despite the increasing use of this tool, little cardiovascular physiology has been quantified across clinically relevant REBOA transitions: placement of occlusive REBOA, then transition to partially occlusive REBOA, and lastly, REBOA removal. The goal of this study is to use pressure-volume loop analysis and direct left coronary artery blood flow measurements to capture these transitions in a swine model of hemorrhagic shock to elucidate the underlying physiologic mechanism of clinical REBOA use. Swine underwent complex surgical and vascular access instrumentation to capture real-time left ventricular pressure-volume loops and directly measure left coronary flow (Figure 1). Animals were hemorrhaged to 45 mmHg with subsequent placement of fully occlusive REBOA, followed by transition to partial REBOA while these data were captured. A full methodological protocol has been published: https://doi.org/10.21203/rs.3.pex-1646/v1. Five male swine underwent this protocol (mean weight, 53.6 ± 3.6 kg). Hemorrhagic shock was induced and maintained with reduction of stroke work (baseline: 3.1 L × mmHg vs shock: 1.2 L × mmHg; P < .01) and average end systolic pressure (109.8 vs 59.6 mmHg; P = .02). REBOA augmented the end systolic pressure volume relationship. Stroke work evolved with placement of occlusive REBOA (1.2 vs 4.3 mmHgL; P < .01). End systolic elastance was augmented from baseline by shock and REBOA placement (1.01 vs 0.39 vs 4.50 mL/mmHg; P < .01) and remained elevated with transition to partial REBOA (3.22 mL/mmHg) (Figure 2). Percent time in antegrade coronary blood flow decreased during shock (94% to 71.8%; P < .01) and was rescued with REBOA, but REBOA also increased peak coronary flow compared with shock (271 vs 93 mL/min; P < .01) and total coronary flow, even beyond baseline (peak: 2136 vs baseline: 424 mL/min; P < .01). No REBOA state augmented the end diastolic pressure volume relationship. REBOA maintains the end diastolic pressure volume relationship, but increases afterload, thereby augmenting the end systolic pressure volume relationship and left ventricle contractility with partial REBOA. REBOA alters coronary artery blood flow by reversing shock-induced retrograde coronary flow, and increasing peak coronary artery flow, therefore increasing total flow. The afterload modulation from REBOA underlies its resuscitative capability but may drive the mechanism of cardiovascular injury. Partial REBOA with resuscitation balances the afterload improvement against undue left ventricle strain.Fig 2End systolic elastance (Ees; the slope of the end systolic pressure volume relationship) evolution across study periods. *P = .003; **P = .048; ***P = .01; ****P = .015.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Pulmonary vascular disease in Fontan circulation-is there a rationale for pulmonary vasodilator therapies?

The Fontan circulation is a palliative concept for patients with univentricular hearts. The central veins are connected directly to the pulmonary arteries (cavo-pulmonary connection) to separate the pulmonary and the systemic circulation. There is no sub-pulmonary ventricle that generates pressure to drive blood through the pulmonary arteries. Pulmonary blood flow is determined by central venous pressure (CVP) and pulmonary vascular resistance (PVR). The capability of the Fontan circulation to compensate for alterations in PVR is limited, as CVP can only be increased within narrow ranges without adverse clinical consequences. Consequently, systemic ventricular preload and cardiac output are dependent on a healthy lung with low PVR. Failure of the Fontan circulation is relatively common. In addition to ventricular dysfunction, maladaptive pulmonary vascular remodeling resulting in increased pulmonary resistance may play a key role. The pathophysiology of the maladaptive vascular processes remains largely unclear and diagnosis of an increased PVR is challenging in Fontan circulation as accurate measurement of pulmonary arterial blood flow is difficult. In the absence of a sub-pulmonary ventricle, pulmonary artery pressure will almost never reach the threshold conventionally used to define pulmonary arterial hypertension. There is a need for markers of pulmonary vascular disease complementary to invasive hemodynamic data in Fontan patients. In order to treat or prevent failure of the Fontan circulation, pathophysiological considerations support the use of pulmonary vasodilators to augment pulmonary blood flow and systemic ventricular preload and lower CVP. However, to date the available trial data have neither yielded enough evidence to support routine use of pulmonary vasodilators in every Fontan patient nor have they been helpful in defining subgroups of patients that might benefit from such therapies. This review discusses potential pathomechanisms of pulmonary vascular disease; it summarizes the current knowledge of the effects and efficacy of pulmonary vasodilator therapy in Fontan patients and tries to outline areas of potential future research on the diagnosis and treatment of pulmonary vascular disease and Fontan failure.

Is stealing still a crime? Comment on left internal mammary artery side branch intervention in the management of coronary steal syndrome following coronary artery bypass grafting

Post-coronary artery bypass graft surgery (CABG) angina has been attributed unligated thoracic side branches competing with LIMA-LAD flow. Case reports suggest thoracic branch occlusion can relieve angina. Phasic arterial blood flow and direct measurements argue against the existence of LIMA steal.

Effect of Pulsed Magnetic Field Therapy Versus Aerobic Training on Peripheral Arteries in Type 2 Diabetes

Abstract Background: Diabetes mellitus is a group of metabolic diseases characterized by high blood glucose levels over a prolonged period of time, requiring continuous medical care and ongoing patient. Self-management education and support, to prevent acute complications and to reduce the risk of long-term complications. Aim of Study: The main purpose of this study was to investigate and compare between the effect of pulsed electro-magnetic field and aerobic exercises in treatment of athero-sclerosis in type 2 diabetic patients. Subjects and Methods: Forty atherosclerotic diabetic patients, with ages ranged from 45 to 55 years old, were recruited from Out Clinic of Faculty of Physical Therapy, Cairo University. They were assigned randomly to two equal groups; group A, which included 20 diabetic atherosclerotic patientswho received PEMF for with 15Hz frequency and 20 gauss intensity for 20min., while group B included 20 diabetic atherosclerotic patients who received aerobic exercise with 65-80% pf predicted max. heart rate. For both groups treatment conducted for 8 weeks, 3 sessions/week. Measurement of arterial blood flow and intimal thickness by Doppler ultra-sonography were reported before and after 8 weeks of the treatment. Results: Within group comparison showed significant increase of arterial blood flow and significant reduction of intimal thickness in both groups in both groups (p < 0.05). Comparison between post-treatment values between both groups showed non-significant difference. Conclusion: It could be concluded that, PEMF and aerobic exercises are effective methods in treatment of arterial problems in type 2 diabetic patients.

Clinical and Radiological Outcomes of Intracranial Aneurysm Clipping Aided by Transit Time Flowmetry

Since the International Subarachnoid Aneurysm Trial, coiling has been favored over clipping for intracranial aneurysms, resulting in selection of increasingly complex aneurysm configurations for clipping. We present the outcomes of clipping of aneurysms not suitable for coiling, with transit time flowmetry technology to aid monitoring of intraoperative flow. All consecutive patients surgically treated for intracranial aneurysms were included. We assessed intraoperative arterial blood flow in relation to postoperative ischemia and unfavorable outcome (modified Rankin Scale score 3-6), along with radiological occlusion rate, at 6 months and 1 year after surgery. Mortality at 1 year was 7.9%, with a 21.6% rate of an unfavorable outcome. Almost all (96.1%) of patients with unruptured aneurysms had an favorable outcome at 1 year, compared with 71.9% of patients with aneurysmal subarachnoid hemorrhage. Postoperative computed tomography imaging showed an 86.7% occlusion rate and a 7.5% rate of clip-related ischemia. Flow <40% of baseline significantly predicted clip-related ischemia (odds ratio [OR], 5.14; 95% confidence interval [CI], 1.41-8.4; P= 0.012). Clip reposition aided by transit time flowmetry resulted in restored flow >50% above baseline flow in 85.7% of aneurysms. Less than 50% flow from baseline was an independent predictor of unfavorable outcome (OR, 3.85; 95% CI, 1.6-9.0; P= 0.001), along other risk factors. In this study of clinical and radiological outcomes of surgically treated cerebral aneurysms not suitable for unassisted coiling, we showed positive results for these challenging aneurysms, aided by transit time flowmetry as a valuable tool, providingquantitative measurements of arterial blood flow to help achieve optimal clip placement and minimizing aneurysm residuals that may be sites of rebleeding. Adequate flow, defined as ≥50% of baseline, greatly reduces the risk of unfavorable outcome.

Ocular blood flow and choroidal thickness changes after carotid artery stenting

To evaluate changes in ocular blood flow and subfoveal choroidal thickness in patients with symptomatic carotid artery stenosis after carotid artery stenting. We included 15 men (mean age, 63.6 ± 9.1 years) with symptomatic carotid artery stenosis and 18 healthy volunteers (all men; mean age, 63.7 ± 5.3 years). All participants underwent detailed ophthalmologic examinations including choroidal thickness measurement using enhanced depth-imaging optic coherence tomography. The patients also underwent posterior ciliary artery blood flow measurements using color Doppler ultrasonography before and after carotid artery stenting. Patients lacked ocular ischemic symptoms. Their peak systolic and end-diastolic velocities increased to 10.1 ± 13.1 (p=0.005) and 3.9 ± 6.3 (p=0.064) cm/s, respectively, after the procedure. Subfoveal choroidal thicknesses were significantly thinner in patients with carotid artery stenosis than those in the healthy controls (p=0.01). But during the first week post-procedure, the subfoveal choroidal thicknesses increased significantly (p=0.04). The peak systolic velocities of the posterior ciliary arteries increased significantly after carotid artery stenting (p=0.005). We found a significant negative correlation between the mean increase in peak systolic velocity values after treatment and the mean preprocedural subfoveal choroidal thickness in the study group (p=0.025, r=-0.617). In patients with carotid artery stenosis, the subfoveal choroid is thinner than that in healthy controls. The subfoveal choroidal thickness increases after carotid artery stenting. Carotid artery stenting treatment increases the blood flow to the posterior ciliary artery, and the preprocedural subfoveal choroidal thickness may be a good predictor of the postprocedural peak systolic velocity of the posterior ciliary artery.

Age-Related Reductions in Cerebrovascular Reactivity Using 4D Flow MRI.

Cerebrovascular reactivity (CVR), is important for determining future risk of cerebrovascular disease. It is unclear if primary aging is associated with reductions in CVR because previous studies often include participants with vascular risk factors. Additionally, the inconsistency in the literature may be due to the inherent difficulty in quantifying intracranial cerebral blood flow and CVR. To address these limitations, we determined the effect of age on CVR in the large intracranial vessels in adults with low vascular risk using state-of-the-art MRI techniques. We also determined if the effect of age on CVR was sex-specific. Young (n = 20; 25 ± 3 years) and older (n = 19; 61 ± 5 years) healthy, physically active adults participated in the study. CVR was measured in response to hypercapnia using 4D flow MRI, which allows for simultaneous angiographic and quantitative blood flow measurements in the intracranial arteries. Older adults had lower global CVR and CVR in multiple intracranial arteries [right and left internal carotid arteries (ICA), right and left middle cerebral arteries (MCA), and basilar artery (BA)] compared with young adults (p < 0.05 for all). In addition, the MCA dilated significantly in response to hypercapnia in young (p < 0.05), but not older adults. Young men demonstrated higher global CVR and CVR in multiple intracranial arteries (ICAs, MCAs, and BA) compared with young women and older men (p < 0.05 for both); however, CVR did not differ between young women and older women. Our results demonstrate that, using 4D flow MRI, primary aging is associated with lower CVR in adults with low vascular risk. In addition, the effect of age on CVR may be driven by men. The 4D flow MRI technique may provide a promising new alternative to measure cerebrovascular physiology without the limitations of commonly used techniques. Future studies could utilize this MRI technique to examine interventions to maintain CVR with advancing age. This study was registered under clinicaltrials.gov # NCT02840851.

Chronic effects of high-intensity interval training on postprandial lipemia in healthy men.

The aim of this study was to determine the chronic (≥72 h postexercise) effects of high-intensity interval training (HIIT) on postprandial lipemia and metabolic markers in healthy volunteers. Eight physically active young men (mean ± SD: age 22 ± 3 yr, height 1.77 ± 0.07 m, body mass 67.7 ± 6.2 kg) underwent two 6-h mixed-meal tolerance tests and resting vastus lateralis muscle biopsies before the first session and ≥72 h after the final session of 4 wk of HIIT [16 sessions in total; 10 × 60-s bouts of cycling at 90% maximal oxygen uptake (V̇o2max), interspersed with 60-s intervals at 45% V̇o2max]. Arterialized and deep venous blood samples from across the forearm, brachial artery blood flow measurements, and whole-body indirect calorimetry data were obtained before, and at regular intervals for 6 h after, consumption of a standardized mixed meal. The main findings revealed that, when assessed ≥72 h postexercise, postprandial free fatty acid (FFA) uptake across the forearm was increased in response to exercise training (P = 0.025). However, 4 wk of HIIT did not alter fasting or postprandial circulating triglyceride concentrations or their tissue uptake, despite a 10.2% ± 7.7% improvement in V̇o2max (P = 0.004). Protein content of adipose triglyceride lipase in the vastus lateralis at rest was reduced by 25% ± 21% (P = 0.01). Collectively, these findings suggest that 4 wk of HIIT enhances postprandial clearance of FFA when assessed ≥72 h postexercise but does not confer persisting (training) adaptations in postprandial triglyceridemia.NEW & NOTEWORTHY When assessed ≥72 h after the last exercise session, 4 wk of high-intensity interval training (HIIT) did not improve triglyceridemia but enhanced free fatty acid uptake into muscle with a concurrent reduction in skeletal muscle adipose triglyceride lipase protein content. This suggests that previously reported acute reductions in postprandial triglyceridemia following a single bout of HIIT do not translate to sustained improvements after 4 wk of HIIT, supporting the concept of frequent exercise for the maintenance of lipemic control.

Blood flow-restricted training enhances thigh glucose uptake during exercise and muscle antioxidant function in humans

This study examined the effects of blood-flow-restricted (BFR)-training on thigh glucose uptake at rest and during exercise in humans and the muscular mechanisms involved. Ten active men (~25 y; VO2max ~50 mL/kg/min) completed six weeks of training, where one leg trained with BFR (cuff pressure: ~180 mmHg) and the other leg without BFR. Before and after training, thigh glucose uptake was determined at rest and during exercise at 25% and 90% of leg incremental peak power output by sampling of femoral arterial and venous blood and measurement of femoral arterial blood flow. Furthermore, resting muscle samples were collected. After training, thigh glucose uptake during exercise was higher than before training only in the BFR-trained leg (p < 0.05) due to increased glucose extraction (p < 0.05). Further, BFR-training substantially improved time to exhaustion during exhaustive exercise (11 ± 5% vs. CON-leg; p = 0.001). After but not before training, NAC infusion attenuated (~50–100%) leg net glucose uptake and extraction during exercise only in the BFR-trained leg, which coincided with an increased muscle abundance of Cu/Zn-SOD (39%), GPX-1 (29%), GLUT4 (28%), and nNOS (18%) (p < 0.05). Training did not affect Mn-SOD, catalase, and VEGF abundance in either leg (p > 0.05), although Mn-SOD was higher in BFR-leg vs. CON-leg after training (p < 0.05). The ratios of p-AMPK-Thr172/AMPK and p-ACC-Ser79/ACC, and p-ACC-Ser79, remained unchanged in both legs (p > 0.05), despite a higher p-AMPK-Thr172 in BFR-leg after training (38%; p < 0.05). In conclusion, BFR-training enhances glucose uptake by exercising muscles in humans probably due to an increase in antioxidant function, GLUT4 abundance, and/or NO availability.

Effects of Dynamic Arm and Leg Exercise on Muscle Sympathetic Nerve Activity and Vascular Conductance in the Inactive Leg

The aim of this study was to comprehensively assess the effects of rhythmic handgrip (RHG), one‐leg cycling, and concurrent arm and leg exercise on muscle sympathetic nerve activity (MSNA) and vascular conductance responses in the inactive leg. Thirty‐five participants completed two study visits in a randomized order. During visit 1, hemodynamic (Finometer) and superficial femoral artery (SFA) blood flow (Doppler ultrasound) measurements were assessed at rest and during 3 min of RHG (1:1 duty cycle; 40% MVC), one‐leg cycling (17 ± 3% peak power output), and concurrent exercise at the same intensities. During visit 2, hemodynamic and MSNA (fibular nerve microneurography) measurements were acquired during the same exercise modes (MSNA; n=12). SFA blood flow and MSNA were both acquired in the inactive leg. Heart rate, blood pressure, cardiac output, and respiration rate increased during each exercise mode (all, P&lt;0.0001), with the largest increases during concurrent exercise (all, P&lt;0.006); no differences were detected between visit 1 and 2 (all, P&gt;0.05). SFA mean blood flow increased during RHG (Δ24 ± 30 ml/min, P&lt;0.0001) and concurrent exercise (Δ10 ± 38 ml/min, P=0.03) but not cycling (Δ2.3 ± 30 ml/min, P=0.9). SFA vascular conductance was unchanged during RHG (Δ0.02 ± 0.29 ml·min−1·mmHg−1, P=0.9) but reduced similarly during concurrent and cycling exercise (Δ−0.14 ± 0.33 ml·min−1·mmHg−1; Δ−0.14 ± 0.38 ml·min−1·mmHg−1, P&lt;0.003). RHG increased MSNA burst frequency (Δ4 ± 8 burst/min, P=0.04) without altering burst amplitude (Δ7 ± 14 %, P=0.7) or total MSNA (Δ40 ± 40 %, P=0.07). In contrast, cycling and concurrent exercise had no effects on MSNA burst frequency (Δ−3 ± 6 burst/min and Δ4 ± 6 burst/min, P≥0.1) but increased burst amplitude (Δ34 ± 30 %; Δ31 ± 31 %, P≤0.001) and total MSNA (Δ59 ± 63 %; Δ94 ± 100 %, P≤0.007). In conclusion, during one‐leg cycling or concurrent exercise, reductions in inactive leg SFA vascular conductance occurred in parallel with increases in burst amplitude and total MSNA but not burst frequency. Exercise studies relying solely on measures of MSNA burst occurrence may not accurately reflect the corresponding changes in vascular conductance.Support or Funding InformationResearch was supported by a Natural Science and Engineering Research Council (NSERC) of Canada Discovery Grant (P.J.M; #06019), the Canada Foundation for Innovation (P.J.M.; #34379), and the Ontario Ministry of Research, Innovation, and Science (P.J.M. #34379).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The Effect of Leg Fidgeting During Sitting on Glycemic Control in Obese Subjects – A Pilot Study

BackgroundProlonged sitting is associated with glycemic excursions, which are likely more pronounced within individuals with risk factors for cardiovascular disease or type 2 diabetes. Strategies to minimize inactivity during sitting are needed to offset its consequences. While chair‐based fidgeting can increase energy expenditure above basal resting metabolic rate, the effect of this minimal amount of physical activity on glycemic control during prolonged sitting has not been investigated. Therefore, the purpose of this ongoing clinical trial is to assess the effect of leg fidgeting during prolonged sitting on glycemic control in obese individuals.DesignFour obese women (43 ± 15 years; BMI = 35 ± 5.9 kg/m2) participated in a randomized cross‐over design study involving two experimental visits. Overnight‐fasted subjects sat in an office chair, ingested a 75 g glucose beverage, and then either refrained from leg movement or performed continuously repeated bouts of bilateral leg fidgeting (2.5 mins of leg fidgeting followed by 2.5 mins of rest) for the next three‐hours. Intravenous blood glucose sampling occurred throughout. Accelerometer data from one leg and popliteal artery blood flow measurements were recorded during the sitting period.ResultsLeg fidgeting resulted in increased accelerometer counts compared to no leg fidgeting (~16‐fold) as designed. In conjunction, leg fidgeting increased popliteal artery blood flow (P&lt;0.05). Each bout of leg fidgeting resulted in elevated blood flow that normalized after 36 seconds (P&lt;0.05) following leg fidgeting cessation. Despite these indicators of increased leg movement and metabolic demand, blood glucose total and incremental area under the curves were not significantly lowered with bilateral leg fidgeting. Blood Glucose concentrations at any time‐point were not different between conditions.ConclusionsLeg fidgeting is not a sufficient stimulus to improve blood glucose concentrations in obese individuals during prolonged periods of physical inactivity, i.e. prolonged sitting. Further investigation is needed to assess more effective physical activity modalities and minimum thresholds of physical activity during sitting to improve blood glucose levels.Support or Funding InformationInstitutional support.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Noninvasive Assessment of Retinal Blood Flow Using a Novel Handheld Laser Speckle Contrast Imager.

PurposeWe assessed the image quality and reproducibility of blood flow measurements from a novel handheld laser speckle imager in handheld and stabilized use cases.MethodsEleven dilated human subjects were imaged with the XyCAM Handheld Retinal Imager investigational device (XyCAM HRI) in the handheld and stabilized use case in nine consecutive imaging sessions. Subjects then underwent standard color fundus photography using a Topcon TRC 50DX. The vessel-to-background contrast of the XyCAM HRI red-free photo was compared to the fundus photograph, while the coefficient of variation of blood flow measurements in specific arteries and veins also was determined.ResultsVessel-to-background contrast was statistically greater in the handheld use case when compared to the standard color fundus photographs (P = 0.01). Estimates of mean blood flow velocity (BFV) were highly correlated between the stabilized and handheld use case (r2 = 0.96). Peak velocity estimates in arteries were significantly higher than those in veins (P < 0.05).ConclusionsThe XyCAM HRI prototype can acquire fundus photographs with the same or better level of clarity as color fundus photographs, and reproducibly acquire functional blood flow information in the handheld use case.Translational RelevanceTo our knowledge, this is the first human study of a handheld laser speckle retinal imaging device. Determination of retinal blood flow has applications to ophthalmic and systemic disease and a portable handheld retinal imager that determines blood flow may be widely adopted at the point of care.

Unilateral application of an external pneumatic compression therapy improves skin blood flow and vascular reactivity bilaterally.

BackgroundWe sought to determine the effects of unilateral lower-limb external pneumatic compression (EPC) on bilateral lower-limb vascular reactivity and skin blood flow.MethodsThirty-two participants completed this two-aim study. In AIM1 (n = 18, age: 25.5 ± 4.7 years; BMI: 25.6 ± 3.5 kg/m2), bilateral femoral artery blood flow and reactivity (flow mediated dilation [FMD]) measurements were performed via ultrasonography at baseline (PRE) and immediately following 30-min of unilateral EPC treatment (POST). AIM2 (n = 14, age: 25.9 ± 4.5; BMI: 27.2 ± 2.7 kg/m2) involved 30-min unilateral EPC (n = 7) or sham (n = 7) treatment with thermographic bilateral lower-limb mean skin temperature (MST) measurements at baseline, 15-min of treatment (T15) and 0, 30 and 60-min (R0, R30, R60) following treatment.ResultsComparative data herein are presented as mean ± 95% confidence interval. AIM1: No significant effects on total reactive hyperemia blood flow were observed for the treated (i.e., compressed) or untreated (i.e., non-compressed) leg. A significant effect of time, but no time*leg interaction, was observed for relative FMD indicating higher reactivity bilaterally with unilateral EPC treatment (FMD: +0.41 ± 0.09% across both legs; p < 0.05). AIM2: Unilateral EPC treatment was associated with significant increases in whole-leg MST from baseline during (T15: +0.63 ± 0.56 °C in the visible untreated/contralateral leg, p < 0.025) and immediately following treatment (i.e., R0) in both treated (+1.53 ± 0.59 °C) and untreated (+0.60 ± 0.45 °C) legs (p < 0.0125). Across both legs, MST remained elevated with EPC at 30-min post-treatment (+0.60 ± 0.45 °C; p < 0.0167) but not at 60-min post (+0.27 ± 0.46 °C; p = 0.165). Sham treatment was associated with a significant increase in the treated leg immediately post-treatment (+1.12 ± 0.31 °C; p < 0.0167), but not in the untreated leg (−0.27 ± 0.12 °C). MST in neither the treated or untreated leg were increased relative to baseline at R30 or R60 (p > 0.05). Finally, during treatment and at all post-treatment time points (i.e., R0, R30 and R60), independent of treatment group (EPC vs. sham), there was a significant effect of region. The maximum increase in MST was observed at the R0 time point and was significantly (p < 0.05) larger in the thigh region (+1.02 ± 0.31 °C) than the lower-leg (+0.47 ± 0.29 °C) region. However, similar rates of MST decline from R0 in the thigh and lower leg regions were observed at the R30 and R60 time points.DiscussionUnilateral EPC may be an effective intervention for increasing skin blood flow and/or peripheral conduit vascular reactivity in the contralateral limb. While EPC was effective in increasing whole-leg MST bilaterally, there appeared to be a more robust response in the thigh compared to the lower-leg. Thus, proximity along the leg may be an important consideration in prospective treatment strategies.

Spatial Configuration of the Uterine Artery Cervical Segment in 3-Dimensional Reconstruction at 11 to 14 Weeks' Gestation.

Uterine artery blood flow measurement is an important component of preeclampsia screening in the first trimester. Transabdominal measurement of the uterine artery pulsatility index has been reported to have relatively low interobserver reproducibility, mainly because the uterine artery is not sampled in the same place every time. We assessed the uterine artery pathway using 3-dimensional power Doppler reconstruction. We found that the artery always forms a loop at the level of the uterine cervix, with anterior descending and posterior ascending segments. The loop spatial position and the appearance of its segments vary according to the parity. In nullipara, the loop is most times regular, with some variations in orientation. It has an anteroposterior position above or at the level of the internal os, and it represents the most inferior point of the uterine artery at this level. In multipara, the loop is almost always rotated; its segments are tortuous and more elongated. The loop is often not the most inferior point of the uterine artery, and its anterior afferent segment sometimes descends below to the level of the loop. Three-dimensional reconstruction can clearly show the appearance of the uterine artery at the level of the cervix. Understanding the spatial arrangement of the uterine artery could enhance the performance of pulsatility index measurement.

Increased tissue oxygenation explains the attenuation of hyperemia upon repetitive pneumatic compression of the lower leg.

The rapid hyperemia evoked by muscle compression is short lived and was recently shown to undergo a rapid decrease even in spite of continuing mechanical stimulation. The present study aims at investigating the mechanisms underlying this attenuation, which include local metabolic mechanisms, desensitization of mechanosensitive pathways, and reduced efficacy of the muscle pump. In 10 healthy subjects, short sequences of mechanical compressions (n = 3-6; 150 mmHg) of the lower leg were delivered at different interstimulus intervals (ranging from 20 to 160 s) through a customized pneumatic device. Hemodynamic monitoring included near-infrared spectroscopy, detecting tissue oxygenation and blood volume in calf muscles, and simultaneous echo-Doppler measurement of arterial (superficial femoral artery) and venous (femoral vein) blood flow. The results indicate that 1) a long-lasting (>100 s) increase in local tissue oxygenation follows compression-induced hyperemia, 2) compression-induced hyperemia exhibits different patterns of attenuation depending on the interstimulus interval, 3) the amplitude of the hyperemia is not correlated with the amount of blood volume displaced by the compression, and 4) the extent of attenuation negatively correlates with tissue oxygenation (r = -0,78, P < 0.05). Increased tissue oxygenation appears to be the key factor for the attenuation of hyperemia upon repetitive compressive stimulation. Tissue oxygenation monitoring is suggested as a useful integration in medical treatments aimed at improving local circulation by repetitive tissue compression.NEW & NOTEWORTHY This study shows that 1) the hyperemia induced by muscle compression produces a long-lasting increase in tissue oxygenation, 2) the hyperemia produced by subsequent muscle compressions exhibits different patterns of attenuation at different interstimulus intervals, and 3) the extent of attenuation of the compression-induced hyperemia is proportional to the level of oxygenation achieved in the tissue. The results support the concept that tissue oxygenation is a key variable in blood flow regulation.