Letteratura scientifica selezionata sul tema "Blood flows indices"
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Articoli di riviste sul tema "Blood flows indices"
1
Kang, Yang Jun. "Microfluidic-Based Biosensor for Sequential Measurement of Blood Pressure and RBC Aggregation Over Continuously Varying Blood Flows". Micromachines 10, n. 9 (30 agosto 2019): 577. http://dx.doi.org/10.3390/mi10090577.
Testo completoAbstract (sommario):
Aggregation of red blood cells (RBCs) varies substantially depending on changes of several factors such as hematocrit, membrane deformability, and plasma proteins. Among these factors, hematocrit has a strong influence on the aggregation of RBCs. Thus, while measuring RBCs aggregation, it is necessary to monitor hematocrit or, additionally, the effect of hematocrit (i.e., blood viscosity or pressure). In this study, the sequential measurement method of pressure and RBC aggregation is proposed by quantifying blood flow (i.e., velocity and image intensity) through a microfluidic device, in which an air-compressed syringe (ACS) is used to control the sample injection. The microfluidic device used is composed of two channels (pressure channel (PC), and blood channel (BC)), an inlet, and an outlet. A single ACS (i.e., air suction = 0.4 mL, blood suction = 0.4 mL, and air compression = 0.3 mL) is employed to supply blood into the microfluidic channel. At an initial time (t < 10 s), the pressure index (PI) is evaluated by analyzing the intensity of microscopy images of blood samples collected inside PC. During blood delivery with ACS, shear rates of blood flows vary continuously over time. After a certain amount of time has elapsed (t > 30 s), two RBC aggregation indices (i.e., SEAI: without information on shear rate, and erythrocyte aggregation index (EAI): with information on shear rate) are quantified by analyzing the image intensity and velocity field of blood flow in BC. According to experimental results, PI depends significantly on the characteristics of the blood samples (i.e., hematocrit or base solutions) and can be used effectively as an alternative to blood viscosity. In addition, SEAI and EAI also depend significantly on the degree of RBC aggregation. In conclusion, on the basis of three indices (two RBC aggregation indices and pressure index), the proposed method is capable of measuring RBCs aggregation consistently using a microfluidic device.
2
Browne, Vaughn A., Colleen G. Julian, Lillian Toledo-Jaldin, Darleen Cioffi-Ragan, Enrique Vargas e Lorna G. Moore. "Uterine artery blood flow, fetal hypoxia and fetal growth". Philosophical Transactions of the Royal Society B: Biological Sciences 370, n. 1663 (5 marzo 2015): 20140068. http://dx.doi.org/10.1098/rstb.2014.0068.
Testo completoAbstract (sommario):
Evolutionary trade-offs required for bipedalism and brain expansion influence the pregnancy rise in uterine artery (UtA) blood flow and, in turn, reproductive success. We consider the importance of UtA blood flow by reviewing its determinants and presenting data from 191 normotensive (normal, n = 125) or hypertensive (preeclampsia (PE) or gestational hypertension (GH), n = 29) Andean residents of very high (4100–4300 m) or low altitude (400 m, n = 37). Prior studies show that UtA blood flow is reduced in pregnancies with intrauterine growth restriction (IUGR) but whether the IUGR is due to resultant fetal hypoxia is unclear. We found higher UtA blood flow and Doppler indices of fetal hypoxia in normotensive women at high versus low altitude but similar fetal growth. UtA blood flow was markedly lower in early-onset PE versus normal high-altitude women, and their fetuses more hypoxic as indicated by lower fetal heart rate, Doppler indices and greater IUGR. We concluded that, despite greater fetal hypoxia, fetal growth was well defended by higher UtA blood flows in normal Andeans at high altitude but when compounded by lower UtA blood flow in early-onset PE, exaggerated fetal hypoxia caused the fetus to respond by decreasing cardiac output and redistributing blood flow to help maintain brain development at the expense of growth elsewhere. We speculate that UtA blood flow is not only an important supply line but also a trigger for stimulating the metabolic and other processes regulating feto-placental metabolism and growth. Studies using the natural laboratory of high altitude are valuable for identifying the physiological and genetic mechanisms involved in human reproductive success.
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Bouhemad, Bélaïd, Fabio Ferrari, Kris Leleu, Charlotte Arbelot, Qin Lu e Jean-Jacques Rouby. "Echocardiographic Doppler Estimation of Pulmonary Artery Pressure in Critically Ill Patients with Severe Hypoxemia". Anesthesiology 108, n. 1 (1 gennaio 2008): 55–62. http://dx.doi.org/10.1097/01.anes.0000296067.02462.34.
Testo completoAbstract (sommario):
Background In spontaneously breathing cardiac patients, pulmonary artery pressure (PAP) can be accurately estimated from the transthoracic Doppler study of pulmonary artery and tricuspid regurgitation blood flows. In critically ill patients on mechanical ventilation for acute lung injury, the interposition of gas between the probe and the heart renders the transthoracic approach problematic. This study was aimed at determining whether the transesophageal approach could offer an alternative. Methods Fifty-one consecutive sedated and ventilated patients with severe hypoxemia (arterial oxygen tension/fraction of inspired oxygen < 300) were prospectively studied. Mean PAP measured from the pulmonary artery catheter was compared with several indices characterizing pulmonary artery blood flow assessed using transesophageal echocardiography: preejection time, acceleration time, ejection duration, preejection time on ejection duration ratio, and acceleration time on ejection duration ratio. In a subgroup of 20 patients, systolic PAP measured from the pulmonary artery catheter immediately before withdrawal was compared with Doppler study of regurgitation tricuspid flow performed immediately after pulmonary artery catheter withdrawal using either the transthoracic or the transesophageal approach. Results Weak and clinically irrelevant correlations were found between mean PAP and indices of pulmonary artery flow. A statistically significant and clinically relevant correlation was found between systolic PAP and regurgitation tricuspid flow. In 3 patients (14%), pulmonary artery pressure could not be assessed echocardiographically. Conclusions In hypoxemic patients on mechanical ventilation, mean PAP cannot be reliably estimated from indices characterizing pulmonary artery blood flow. Systolic PAP can be estimated from regurgitation tricuspid flow using either transthoracic or transesophageal approach.
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Kang, Yang. "A Disposable Blood-on-a-Chip for Simultaneous Measurement of Multiple Biophysical Properties". Micromachines 9, n. 10 (20 settembre 2018): 475. http://dx.doi.org/10.3390/mi9100475.
Testo completoAbstract (sommario):
Biophysical properties are widely used to detect pathophysiological processes of vascular diseases or clinical states. For early detection of cardiovascular diseases, it is necessary to simultaneously measure multiple biophysical properties in a microfluidic environment. However, a microfluidic-based technique for measuring multiple biophysical properties has not been demonstrated. In this study, a simple measurement method was suggested to quantify three biophysical properties of blood, including red blood cell (RBC) deformability, RBC aggregation, and hematocrit. To demonstrate the suggested method, a microfluidic device was constructed, being composed of a big-sized channel (BC), a parallel micropillar (MP), a main channel, a branch channel, inlet, and outlets. By operating a single syringe pump, blood was supplied into the inlet of the microfluidic device, at a periodic on-off profile (i.e., period = 240 s). The RBC deformability index (DI) was obtained by analyzing the averaged blood velocity in the branch channel. Additionally, the RBC aggregation index (AIN) and the hematocrit index (HiBC) were measured by analyzing the image intensity of blood flows in the MP and the BC, respectively. The corresponding contributions of three influencing factors, including the turn-on time (Ton), the amplitude of blood flow rate (Q0), and the hematocrit (Hct) on the biophysical indices (DI, AIN, and HiBC) were evaluated quantitatively. As the three biophysical indices varied significantly with respect to the three factors, the following conditions (i.e., Ton = 210 s, Q0 = 1 mL/h, and Hct = 50%) were maintained for consistent measurement of biophysical properties. The proposed method was employed to detect variations of biophysical properties depending on the concentrations of autologous plasma, homogeneous hardened RBCs, and heterogeneous hardened RBCs. Based on the observations, the proposed method exhibited significant differences in biophysical properties depending on base solutions, homogeneous hardened RBCs (i.e., all RBCs fixed with the same concentration of glutaraldehyde solution), and heterogeneous hardened RBCs (i.e., partially mixed with normal RBCs and homogeneous hardened RBCs). Additionally, the suggested indices (i.e., DI, AIN, and HiBC) were effectively employed to quantify three biophysical properties, including RBC deformability, RBC aggregation, and hematocrit.
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Toubaei, S. "Blood Flow of Carotid Arteries in Schizophrenic Patients". European Psychiatry 24, S1 (gennaio 2009): 1. http://dx.doi.org/10.1016/s0924-9338(09)71439-7.
Testo completoAbstract (sommario):
Background:Based on new imaging, some results have led to the hypothesis, indicating left hemispheric dysfunction in schizophrenic patients,Transcranial color Doppler sonography also showed significant blood flow velocity changes in schizophrenic patients.Our study tried to clarify possible differences between carotid blood flow of each side, in symptom positive and symptom negative schizophrenic patients, as well as differences of blood flow between schizophrenic patients versus control cases.Methods:31 schizophrenic patients which had been selected randomly were divided in two separate groups of symptom positive (14 cases) and symptom negative (17 cases) patients, according to PANSS test. Then carotid color Doppler sonography was performed for them and for 32 control cases.Velosities (PSV, DV) and Doppler indices (RL, PI) were measured to be compared statistically in patients and control cases.Results:According to P value < 0.05 as level of significance in all comparisons, no evidence of any significant differences is seen between two sides of patients(positive symptoms and negative symptoms) as though between control cases and patients. No positive conclusion also derived based on sex interference.Conclusion:So examination reveals no differences between carotid blood flows of two sides in schizophrenic patients(positive and negative symptom).There is no differences between carotid blood flow of patients and control group, even when sex interfered as a variety.
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Tiederman, W. G., M. J. Steinle e W. M. Phillips. "Two-Component Laser Velocimeter Measurements Downstream of Heart Valve Prostheses in Pulsatile Flow". Journal of Biomechanical Engineering 108, n. 1 (1 febbraio 1986): 59–64. http://dx.doi.org/10.1115/1.3138581.
Testo completoAbstract (sommario):
Elevated turbulent shear stresses resulting from disturbed blood flow through prosthetic heart valves can cause damage to red blood cells and platelets. The purpose of this study was to measure the turbulent shear stresses occurring downstream of aortic prosthetic valves during in-vitro pulsatile flow. By matching the indices of refraction of the blood analog fluid and model aorta, correlated, simultaneous two-component laser velocimeter measurements of the axial and radial velocity components were made immediately downstream of two aortic prosthetic valves. Velocity data were ensemble averaged over 200 or more cycles for a 15-ms window opened at peak systolic flow. The systolic duration for cardiac flows of 8.4 L/min was 200 ms. Ensemble-averaged total shear stress levels of 2820 dynes/cm2 and 2070 dynes/cm2 were found downstream of a trileaflet valve and a tilting disk valve, respectively. These shear stress levels decreased with axial distance downstream much faster for the tilting disk valve than for the trileaflet valve.
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Gelsomino, Sandro, Pieter Willem Lozekoot, Roberto Lorusso, Monique Maria de Jong, Orlando Parise, Francesco Matteucci, Fabiana Lucà et al. "A New 35-mm Short Intra-aortic Balloon Catheter: A Suitable Option also for Non-Small-Sized Patients?" Innovations: Technology and Techniques in Cardiothoracic and Vascular Surgery 11, n. 1 (gennaio 2016): 46–53. http://dx.doi.org/10.1097/imi.0000000000000233.
Testo completoAbstract (sommario):
Objective Visceral ischemia can be a potentially life-threatening complication of intra-aortic balloon pump (IABP) support. A shorter IABP catheter might lead to a reduction of visceral complications. In this animal study, we evaluate the effects of a 35-mL short catheter in comparison with a 40-mL standard-sized catheter. Methods Eighteen healthy swine underwent 120-minute ligation of the left anterior descending coronary artery followed by 6 hours of reperfusion being supported by either a short IABP catheter (short group) (n = 6) or a long IABP catheter (long group) (n = 6) or with no assistance (controls) (n = 6). Hemodynamics, visceral and coronary flows, as well as biochemical markers were evaluated throughout the different phases of the protocol. Results Mesenteric flows increased significantly at reperfusion (P < 0.001 both) remaining constant afterward (all, P > 0.05) in the short group, while remaining significantly lower in the long group at the start of reperfusion, remaining constantly lower than the short group and controls (P < 0.001 vs short, P < 0.003 vs controls). In both long and short groups, catheters improved renal flows at reperfusion (P < 0.001 both) without any further variation (P < 0.05). In the short group, the flows were higher during the whole of reperfusion (all, P < 0.05). Intra-aortic balloon pump support improved hemodynamic indices and coronary blood flows during reperfusion to a similar extent in both the small and the long group (P > 0.05). Conclusions The short IABP catheter proved to be as effective as the standard-sized catheter in supporting hemodynamics and coronary circulation. Furthermore, it even improves visceral flows in comparison with conventional IABP catheters.
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Mandolfo, S., F. Galli, S. Costa, P. Ravani, P. Gaggia e E. Imbasciati. "Factors Influencing Permanent Catheter Performance". Journal of Vascular Access 2, n. 3 (luglio 2001): 106–9. http://dx.doi.org/10.1177/112972980100200304.
Testo completoAbstract (sommario):
Permanent dual lumen catheters (PDLC) provide an alternative vascular access in patients considered unsuitable for arteriovenous fistula, graft or peritoneal dialysis. However, the use of PDLC is often complicated by inadequate blood flow. The aim of this study was to identify catheter dysfunctions. We studied prospectively 57 chronic hemodialyzed patients, 73±11 years of age, with PDLC for 18±14 (1–48) months. Catheters were tunneled in silicone (MedComp Tesio n= 40) or in polyurethane (Permcath Quinton n = 11, GamCath Gambro n = 6) in left or right internal jugular (n = 49), in left or right subclavian (n = 3) and in right femoral vein (n = 5). We studied the blood viscosity indices (hematocrit, total protein, cholesterol and triglycerides), catheter intra-dialytic parameters (pre-pump and venous pressure), localization of the catheter tip (superior vena cava = SVC, right atrium = RA, inferior vena cava = IVC), blood pressure before and after hemodialysis during the 3 last dialyses, use of anticoagulant (ACT) or antiaggregant therapy (AAT) and previous infectious episodes. The mean blood flow was 269±37 ml/min (median 280 ml/min). The patients were divided according to the median value into groups I (Qb < 280, n = 28) and group II (Qb > 280, n =29). Results: Blood viscosity, patients’ mean arterial pressure and venous catheter line pressure did not differ between the two groups. Pre-pump pressure, at the start and at the end of treatment, was higher in group I. ACT, AAT and previous infectious episodes could not explain the low-performance. Blood flows of catheters localized in RA, SVC, and in IVC were respectively 287±20, 268±39, 244±27 ml/min. In the first case the Qb was significantly higher than IVC (p = 0.03) and SVC (p = 0.04). In conclusion, the most important factor influencing blood flow rates seems to be the position of the catheter tip in the venous system. The best blood flows were found in catheters with the tip localized in the right cardiac cavities, while PLDC placed in inferior vena cava showed lower blood flow.
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Hazari, Vajihe, Fatemeh Sarvi, Ashraf Alyasin, Marzieh Agha-Hosseini e Sedigheh Hosseinimousa. "Effectiveness the perfusion of Endometrial and Subendometrial and Endometrial volume on the endometrial receptivity of FET Cycles". Obstetrics Gynecology and Reproductive Sciences 5, n. 7 (25 settembre 2021): 01–06. http://dx.doi.org/10.31579/2578-8965/067.
Testo completoAbstract (sommario):
Objective: this study was effects of endometrial and subendometrial blood perfusion and endometrial volume on endometrial receptivity in frozen embryo transfer (FET) cycles. Materials and methods: This prospective observational cohort study, that on infertile women who referred for FET to Shariati Hospital and Omid Infertility Clinic in Tehran (Iran) .112 patients selected among eligible women with good quality embryos. After homogenization, participants underwent endometrial preparation for hormone replacement therapy (HRT) according to a similar routine protocol. On the day of the FET, they underwent a thorough ultrasound examination for possible effective parameters. Subsequently, one to two good quality blastocysts were transferred, and the pregnancy outcomes were monitored. Results: In vitro fertilization (IVF) was performed on 112 patients with a mean age of 33.93±4.93 years. Although, serum β-HCG level was used to confirm pregnancy. Accordingly, out of 112 participating patients, 50 (44.6%) became pregnant after IVF. Based on the results of this study, the endometrial blood flow was significantly different between the two groups of pregnant and non-pregnant women, so that a higher pregnancy rate was observed in participants with multi-focal and spare endometrial blood flows (P<0.05). Additionally, a significant relationship between endometrial blood flow and pregnancy outcome so that there was more ongoing pregnancy rates in those with multi-focal and spare endometrial blood flows (P<0.05). But the endometrial variables of volume, length, width, thickness and pattern were not significantly different between the two groups of pregnant and non-pregnant women. Moreover, contextual parameters had no significant relationship with pregnancy outcome (P>0.05). Endometrial measurement indices were also ineffective on pregnancy outcomes and no significant difference was there between the groups (P>0.05). Conclusion: Collectively, the endometrial blood flow can play an effective role in improving pregnancy event and its stability after IVF, but the endometrial volume was unable to predict pregnancy event and its stability after IVF.
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Nestola, Maria G. C., Alessio Gizzi, Christian Cherubini e Simonetta Filippi. "Three-band decomposition analysis in multiscale FSI models of abdominal aortic aneurysms". International Journal of Modern Physics C 27, n. 02 (23 dicembre 2015): 1650017. http://dx.doi.org/10.1142/s0129183116500170.
Testo completoAbstract (sommario):
Computational modeling plays an important role in biology and medicine to assess the effects of hemodynamic alterations in the onset and development of vascular pathologies. Synthetic analytic indices are of primary importance for a reliable and effective a priori identification of the risk. In this scenario, we propose a multiscale fluid-structure interaction (FSI) modeling approach of hemodynamic flows, extending the recently introduced three-band decomposition (TBD) analysis for moving domains. A quantitative comparison is performed with respect to the most common hemodynamic risk indicators in a systematic manner. We demonstrate the reliability of the TBD methodology also for deformable domains by assuming a hyperelastic formulation of the arterial wall and a Newtonian approximation of the blood flow. Numerical simulations are performed for physiologic and pathologic axially symmetric geometry models with particular attention to abdominal aortic aneurysms (AAAs). Risk assessment, limitations and perspectives are finally discussed.
Tesi sul tema "Blood flows indices"
1
Kumar, Hemant, University of Western Sydney e of Science Technology and Environment College. "Software analytical tool for assessing cardiac blood flow parameters". THESIS_FSTA_XXX_Kumar_H.xml, 2001. http://handle.uws.edu.au:8081/1959.7/392.
Testo completoAbstract (sommario):
Introduction of Doppler ultrasound techniques into the Intensive Care setting has revolutionised the way haemodynamic status is monitored in the critically ill. However, in order to increase the usefulness of these techniques, the Doppler signal and its spectrum need to be further analysed in ways to facilitate a better clinical response. Extensive processing of the Doppler spectrum on Diagnostic ultrasound machines is limited by the real time performance considerations. It was therefore proposed that the spectral information from these systems be extracted off-line and full set of analytical tools be made available to evaluate this information. This was achieved by creating an integrated and modular software tool called Spectron, which was intended as an aid in the overall management of the patients. The modular nature of Spectron was intended to ensure that new analytical tools and techniques could be easily added and tested. The software provides its users with considerable latitude in choosing various data acquisition and analysis parameters to suit various clinical situations and patient requirements. Spectron was developed under the Windows environment to provide a user friendly interface and to address a range of programming problems such as memory management and the size of the colour palettes. Spectron is able to detect the maximal velocities and compute the mean and median velocities. Relative increases in maximal velocities in cardiac blood flows after the administration of inotropic drugs have been shown in the pilot studies that were conducted. Spectron is able to help in obtaining estimates of the aortic blood flows and in other applications such measuring vascular impedance. Stenotic blood flows can be detected by using the spectral broadening index and blood flow characteristics can be studied by using various blood flow indices. Thus, this project attempted to help in patient management by providing clinicians with a range of blood flow parameters and has succeeded in meeting its objective to a large extentMaster of Engineering (Hons)
2
Kumar, Hemant. "Software analytical tool for assessing cardiac blood flow parameters". Thesis, View thesis, 2001. http://handle.uws.edu.au:8081/1959.7/392.
Testo completoAbstract (sommario):
Introduction of Doppler ultrasound techniques into the Intensive Care setting has revolutionised the way haemodynamic status is monitored in the critically ill. However, in order to increase the usefulness of these techniques, the Doppler signal and its spectrum need to be further analysed in ways to facilitate a better clinical response. Extensive processing of the Doppler spectrum on Diagnostic ultrasound machines is limited by the real time performance considerations. It was therefore proposed that the spectral information from these systems be extracted off-line and full set of analytical tools be made available to evaluate this information. This was achieved by creating an integrated and modular software tool called Spectron, which was intended as an aid in the overall management of the patients. The modular nature of Spectron was intended to ensure that new analytical tools and techniques could be easily added and tested. The software provides its users with considerable latitude in choosing various data acquisition and analysis parameters to suit various clinical situations and patient requirements. Spectron was developed under the Windows environment to provide a user friendly interface and to address a range of programming problems such as memory management and the size of the colour palettes. Spectron is able to detect the maximal velocities and compute the mean and median velocities. Relative increases in maximal velocities in cardiac blood flows after the administration of inotropic drugs have been shown in the pilot studies that were conducted. Spectron is able to help in obtaining estimates of the aortic blood flows and in other applications such measuring vascular impedance. Stenotic blood flows can be detected by using the spectral broadening index and blood flow characteristics can be studied by using various blood flow indices. Thus, this project attempted to help in patient management by providing clinicians with a range of blood flow parameters and has succeeded in meeting its objective to a large extent
3
Machado, Maria Virginia Lima. "Doppler blood flow indices in fetal and early neonatal life". Thesis, King's College London (University of London), 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.689608.
Testo completo
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Reinerman, Lauren E. Ph D. "Cerebral Blood Flow Velocity and Stress Indices as Predictors of Cognitive Vigilance Performance". University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1212092469.
Testo completo
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França, Itamara Gomes de. "Efeito do escore do trato reprodutivo na dinâmica folicular e dopplerfluxometria útero-ovariana em novilhas nelore (Bos indicus)". Universidade Federal do Maranhão, 2016. http://tedebc.ufma.br:8080/jspui/handle/tede/1697.
Testo completoAbstract (sommario):
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ItamaraFranca.pdf: 611104 bytes, checksum: 4827358f1120e6b66cf862bb0635763f (MD5)Made available in DSpace on 2017-06-26T17:30:38Z (GMT). No. of bitstreams: 1 ItamaraFranca.pdf: 611104 bytes, checksum: 4827358f1120e6b66cf862bb0635763f (MD5) Previous issue date: 2016-08-31
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão (FAPEMA)
The objective of this study was to evaluate the effect of the reproductive tract scoring (RTS) on follicular dynamics and utero-ovarian doppleflowmetry in Bos indicus heifers of nelore. Were used 34 females cattle the females were classified into three categories, according to RTS: RTS 1 (diameter of the uterine horns <15 mm and diameter of follicles <8 mm; RTS 2 (diameter of the uterine horns ≥ 15mm and follicles ≥8 mm; RTS3 (diameter of the uterine horns ≥15mm and presence of CL). Then, were synchronized with progestin/estradiol-based protocol, plus prostaglandin, for padronization of the follicular and luteal status. The monitoring of the follicular dynamics and utero-ovarian flowmetry was performed by B-mode, color doppler and spectral doppler ultrasonography during three times: Day 0 (D0; ear implant insertion); Day 10 (D10, detection preovulatory follicles) and; Day 18 (D18; determination of ovulation by detection of corpora lutea). The uterine diameter showed a significant increase between D0 and D10 in both categories. The ovulation rate was higher in the RTS 3 (P<0.05). There was no effect of RTS nor of examination day on vascularity and number of pixels of the the ovary (P>0.05). In the follicular dominance phase (D10), the higher vascularization occurred in RTS2, followed by RTS 1 and 3, respectively (P<0.05). The uterine PI and RI were not affected by RTS nor by the examination day (P>0.05). However, when these same rates were evaluated in the ovary, the RI showed significant effect of RTS and RTS x day (P=0.02). Progesterone concentrations at the beginning of trial (D0) were higher in the RTS 3 (P<0.05) and estradiol did not differ significantly between categories (P<0.05) at day of follicular dominance (D10). It was concluded that RTS influences the follicular growth, ovulation rate and vascularization of the uterine horns.
Objetivou-se com este estudo avaliar o efeito do escore do trato reprodutivo (ETR) na dinâmica folicular e dopplerfluxometria útero-ovariana em novilhas da raça nelore (Bos indicus). Utilizou-se 34 fêmeas que foram classificadas em três categorias, de acordo com o ETR: ETR 1 (novilhas com diâmetro dos cornos uterinos <15mm e com folículos de diâmetro <8mm; ETR2 (novilhas com diâmetro dos cornos uterinos ≥ 15mm e folículos ≥8 mm e; ETR3 (novilhas com diâmetro dos cornos uterinos ≥15mm e presença de corpo lúteo (CL). Em seguida, foram sincronizadas com protocolo à base de progestágeno/estradiol/prostaglandina para padronização do status folicular e luteínico. O acompanhamento da dinâmica folicular e fluxometria útero-ovariana foram realizadas por ultrassonografia (US) nos modos bidimensional, color doppler e espectral doppler em 3 períodos pré-determinados: Dia 0 (D0; inserção do implante auricular); Dia 10 (D10; detecção folículo pré-ovulatório) e; Dia 18 (D18; determinação da ovulação por meio da detecção do corpo lúteo). O diâmetro uterino apresentou um aumento significativo entre o D0 e D10 em ambas as categorias. A taxa de ovulação foi maior no ETR 3 (P<0,05). Não houve efeito de ETR ou dia de exame na área de vascularização e número de pixels no ovário (P>0,05). Na fase de dominância folicular (D10), a maior perfusão ocorreu no ETR2, seguida pelos ETRs 1 e 3, respectivamente (P<0,05). O IP e o IR uterinos não foram influenciados pelo ETR nem pelo dia do exame (P>0,05). Entretanto, quando estes mesmos índices foram avaliados no ovário, nota-se que o RI manifestou efeito significativo do ETR e interação ETR x dia do exame (P=0,02). As concentrações plasmáticas de progesterona ao início do experimento (D0) foram maiores no ETR 3 (P<0,05) e o estradiol não diferiu significativamente entre as categorias (P<0,05) na fase de dominância folicular sincronizada (D10). Conclui-se que o ETR influencia no crescimento folicular, na taxa de ovulação e na vascularização dos cornos uterinos.
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Papievienė, Vilma. "Peculiarities of concatenation between cardiovascular functional indices while performing increasing workload up to inability to continue the task". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20140520_085358-54570.
Testo completoAbstract (sommario):
Since the analysis of dynamics of intervals of short cardiovascular signals reflects important vital processes, involving complex interactions of the regulatory processes (Batzel, Bachar, 2010), mathematical formalism is one of the ways to research the complexity of biological systems (Davis et al., 2010). Concerning the interaction of various physiological systems / parameters that point out the causes of fatigue, the theory of non-linear dynamical systems enables to reveal this phenomenon as a part of dynamic system’s processes.
Cardiovascular functional values are integral indicators, i.e. the values of the recorded parameters are affected by numerous factors or at least some of them. The question to which we tried to find the answer performing the following analysis of the data could be worded as follows. Apparently, the evaluation of the dynamic concatenation among these cardiovascular parameters, when the functional state of the subject changes, can reveal an increase or decrease in the significance of the selected structural component during the developing and incremental fatigue. The aim of the study was to find out the peculiarities in concatenation between central and peripheral cardiovascular indices under the conditions of increasing fatigue.
Objectives:
1. To compare the peculiarities of dynamics in cardiovascular functional and functional state indices while performing increamental exercise up to inability by applying the provocative or increasing workload... [to full text]Nauji tyrimų rezultatų analizės metodai, nauja tyrimų metodologija išplečia fiziologų galimybes pažinti naujas, ligi šiol neatskleistas organizmo funkcijų ypatybes, panaudoti jas funkcinei būklei vertinti, valdant fizinio ir kitokio poveikio trukmę, stiprumą, ieškant optimalaus poveikio ir adaptacijos efekto. Kompleksiškumo ypatybėms vertinti Lietuvos mokslininkai pasiūlė dinaminių sąsajų vertinimo metodiką, taikant algebrinį duomenų kointegracijos metodą (Navickas ir kt., 2005; Navickas, Bikulčienė, 2008; Vainoras et al., 2008; Bikulčienė et al., 2009; Poderys et al., 2010). Darbo tikslas – nustatyti aktyvių raumenų kraujotakos ir kitų ŠKS funkcinių rodiklių dinaminių sąsajų ypatybes atliekant didėjantį fizinį krūvį iki negalėjimo. Uždaviniai: 1. Palyginti ŠKS funkcinių ir funkcinės būklės rodiklių kaitos ypatybes atliekant pakopomis didėjantį fizinį krūvį iki negalėjimo, taikant provokacinio ir darbinio fizinio krūvio didinimo protokolus. 2. Nustatyti reikšmingų širdies ir kraujagyslių sistemos funkcinių rodiklių dinaminių sąsajų ypatybes veloergometru atliekant pakopomis didėjantį fizinį krūvį iki negalėjimo. 3. Nustatyti adaptacijos greitumo, arba ištvermės fiziniams krūviams, įtaką širdies ir kraujagyslių sistemos funkcinių rodiklių dinaminių sąsajų kaitai atliekant pakopomis didėjantį fizinį krūvį iki negalėjimo. 4. Nustatyti, ar galima algebriniu duomenų kointegracijos metodu gauti fiziologijai reikšmingą informaciją, vertinant dinamines sąsajas tarp rodiklių, kai... [toliau žr. visą tekstą]
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Gargano, Ronaldo Gomes. "Ultrassonografia Doppler do fluxo arterial digital associado à alteração do coxim digital dos bovinos". Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/10/10136/tde-07102015-105755/.
Testo completoAbstract (sommario):
O objetivo do estudo foi avaliar, por meio da ultrassonografia bidimensional e da ultrassonografia Doppler, as inter-relações entre a alteração de espessura do coxim digital com os índices vasculares da artéria digital dorsal comum dos membros pélvicos dos bovinos. A avaliação ultrassonográfica Doppler é uma técnica não invasiva de avaliação de índices vasculares, assim como, indiretamente, do volume de sangue do leito vascular. Para isso, foram realizados exames ultrassonográficos da espessura do coxim digital e também avaliação ultrassonográfica Doppler da referida artéria de 13 vacas primíparas da raça Holandesa, em intervalos de 14 dias, durante 126 dias após o parto. Ao longo do experimento o coxim digital apresentou diminuição não significativa de espessura (p=0,1715) e apresentou forte correlação positiva com a média do escore de condição corporal (p=0,03, r=0,71). Ao longo do período avaliado, o fluxo de sangue aumentou significativamente (p<0,0001) e apresentou correlação negativa com os índices que denotam impedância ao deslocamento de sangue, isto é, índice de resistividade (p<0,0001, r=-0,34911) e pulsatilidade (p<0,0001, r=-0,5035). Além disso, realizou-se correlação entre a diferença diária do fluxo de sangue e a diferença da espessura do coxim digital para cada animal e constatou-se uma forte tendência à correlação entre as diferenças das variáveis (p=0,0515, r=-0,5729). Por meio dos resultados encontrados foi possível concluir que o escore de condição corporal teve forte correlação com a espessura do coxim digital, ao longo do estudo. Além disso, o fluxo de sangue, os índices referentes à velocidade de deslocamento das hemácias e o diâmetro da artéria aumentaram ao longo do trabalho. E, também, que a discreta diminuição do coxim digital não foi um fator que influenciou no aumento do fluxo de sangue e nos índices vascularesThe aim of this study was to evaluate, by bidimensional and pused Doppler ultrasound, the interrelationship between the changes of the thickness of digital cushion with vascular indices of the common dorsal digital artery of the hind limbs of cattle. Pused Doppler sonography is a non-invasive tool to assessment the vascular indices, as well as, the blood flow volume in vascular bed. So, were performed ultrasound exams of soft tissue thickness and also the Doppler ultrasonographic evaluation of that artery in thirteen first lactation Holstein cows and followed them up during 126 days in milk. Throughout the experiment the digital cushion showed a slight decrease without significance (p=0,1715), this also was strongly correlated with body condition score (p=0,03, r=0,71). The blood flow volume had significance increase (p<0,0001) and was negatively correlated with both impedance indices, resistance index (P<0,0001 r =-0,34911) and pulsatility index (p <0,0001 r =-0,5035). In addition, a correlation was performed with both daily differences of the blood flow and the thickness of the digital cushion for each animal and it was observed a strong tendency of correlation between the different variables (p=0,0515 r =-0,5729). Therefore, we can conclude that body condition score was strong correlated with the thickness of digital cushion, throughout the study. In addition, the blood flow volume, the velocity indices and the artery diameter increase throughout the days in milk. And, so, the slight decrease in the thickness of digital cushion was not a factor that influenced the increase of blood flow and vascular indices
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Jouette, Christian. "Conception d'un appareil de mesure du débit sanguin tissulaire par effet doppler optique : choix des paramètres d'échantillonnage et d'analyse spectrale, et détermination d'un indice débit métrique". Nancy 1, 1994. http://www.theses.fr/1994NAN10106.
Testo completoAbstract (sommario):
La mesure du débit sanguin tissulaire par effet doppler optique est une idée séduisante. L'utilisation d'une source laser, par la cohérence spatiale et géométrique qu'elle offre, en simplifie la réalisation pratique. La vitesse des différentes composantes, notamment les hématies, n'est pas uniforme. Il en résulte donc une distribution spectrale image de cette répartition. De plus, l'environnement du faisceau laser étant constitué par de la matière vivante, de nombreux paramètres influencent les résultats. Dans un premier temps, nous décrivons l'évolution des doppler-lasers, et nous exposons les problèmes qu'ils soulèvent. Ceci nous amène à considérer ensuite, que seule une étude fine du spectre peut nous conduire à un appareil fiable et réellement utilisable en routine. Nous présentons ici un doppler-laser à traitement numérique. La distribution spectrale est calculée par un processeur de signaux numérique (dsp) grâce à un algorithme de transformée de Fourier rapide. Nous donnons les paramètres caractéristiques qui nous paraissent optimaux, et relevons les difficultés qui subsistent avant de pouvoir réaliser un système performant
Libri sul tema "Blood flows indices"
1
The River of blood flows on. Toronto: Published by Rojo Nuevo Collective/Red Tree in association with A Space, 1992.
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Kellum, John A. Diagnosis of oliguria and acute kidney injury. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199600830.003.0212.
Testo completoAbstract (sommario):
Diagnosis and classification of acute pathology in the kidney is major clinical problem. Azotemia and oliguria represent not only disease, but also normal responses of the kidney to extracellular volume depletion or a decreased renal blood flow. Clinicians routinely make inferences about both the presence of renal dysfunction and its cause. Pure prerenal physiology is unusual in hospitalized patients and its effects are not necessary benign. Sepsismay alter renal function without the characteristic changes in urine indices. The clinical syndrome known as acute tubular necrosis does not actually manifest the histological changes that the name implies. Acute kidney injury (AKI) is a term proposed to encompass the entire spectrum of the syndrome from minor changes in renal function to a requirement for renal replacement therapy. Criteria based on both changes in serum creatinine and urine output represent a broad international consensus for diagnosing and staging AKI.
Capitoli di libri sul tema "Blood flows indices"
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Obrist, W. D., e W. E. Wilkinson. "Stability and Sensitivity of CBF Indices in the Noninvasive 133Xe Method". In Cerebral Blood Flow and Metabolism Measurement, 30–36. Berlin, Heidelberg: Springer Berlin Heidelberg, 1985. http://dx.doi.org/10.1007/978-3-642-70054-5_4.
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Piechnik, Stefan, M. Czosnyka, P. Smielewski e J. D. Pickard. "Indices for Decreased Cerebral Blood Flow Control — A Modelling Study". In Intracranial Pressure and Neuromonitoring in Brain Injury, 269–71. Vienna: Springer Vienna, 1998. http://dx.doi.org/10.1007/978-3-7091-6475-4_78.
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Ciccarelli, Giovanni, Emanuele Barbato e Bernard De Bruyne. "Fractional flow reserve". In State of the Art Surgical Coronary Revascularization, a cura di David P. Taggart, John D. Puskas e Mario Gaudino, 63–67. Oxford University Press, 2021. http://dx.doi.org/10.1093/med/9780198758785.003.0017.
Testo completoAbstract (sommario):
Fractional flow reserve is an index of the physiological significance of a coronary stenosis, defined as the ratio of maximal myocardial blood flow in the presence of the stenosis to the theoretically normal maximal myocardial blood flow (i.e. in the absence of the stenosis). This flow ratio can be calculated from the ratio of distal coronary pressure to central aortic pressure during maximal hyperaemia. More practically, fractional flow reserve indicates to what extent the epicardial segment can be responsible for myocardial ischaemia and, accordingly, fractional flow reserve quantifies the expected perfusion benefit from revascularization by percutaneous coronary intervention. Very limited evidence exists on the role on fractional flow reserve for bypass grafts.
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Alexis-Ruiz, Adrian, e Marisa Cevasco. "Right Ventricular Assist Device Therapies". In Cardiothoracic Critical Care, 215–20. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780190082482.003.0022.
Testo completoAbstract (sommario):
This chapter discusses right ventricular assist device (RVAD) therapies. Current RVAD options include the Impella Right Peripheral, the Tandem Heart, the Protek Duo system, and a surgically placed CentriMag RVAD. Important considerations when choosing a device include operator familiarity, the need for an oxygenator, the availability of a surgeon, and specific contraindications such as severe tricuspid regurgitation, an occluded internal jugular vein, or the presence of an inferior vena cava filter. It is important to consider the hemodynamic effects on the left ventricle (LV) after placement of an RVAD. Identifying biventricular failure early is critical when RVAD implantation is considered. RVADs reduce right atrial pressure, increase flow through the pulmonary arteries, and increase LV preload and wedge pressure. This change in preload may worsen LV function and cause pulmonary edema in patients with LV failure. LV assist device revolutions per minute may need to increase after placement of an RVAD to manage increased flow to the LV. Ultimately, assessing changes in oxygen saturation, blood pressure, and echocardiographic indices can guide hemodynamic management of RVAD therapy.
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Morrell, Nicholas W. "Pulmonary hypertension". In Oxford Textbook of Medicine, a cura di Jeremy Dwight, 3695–710. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780198746690.003.0374.
Testo completoAbstract (sommario):
Symptoms of unexplained exertional breathlessness or symptoms out of proportion to coexistent heart or lung disease should alert the clinician to the possibility of pulmonary hypertension, and the condition should be actively sought in patients with known associated conditions, such as scleroderma, hypoxic lung disease, liver disease, or congenital heart disease. Heterozygous germ-line mutations in the gene encoding the bone morphogenetic protein type II receptor (BMPR2) are found in over 70% of families with pulmonary arterial hypertension. Pulmonary hypertension is defined as a mean pulmonary arterial pressure greater than 25 mm Hg at rest, and may be due to increased pulmonary vascular resistance (e.g. pulmonary arterial hypertension), increased transpulmonary blood flow (e.g. congenital heart disease), or increased pulmonary venous pressures (e.g. mitral stenosis). Exercise tolerance and survival in pulmonary hypertension is ultimately related to indices of right heart function, such as cardiac output.
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Singha, Radhika. "Making the Desert Bloom?" In The Coolie's Great War, 95–158. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780197525586.003.0004.
Testo completoAbstract (sommario):
World War one witnessed the first dense flow of Indian labor into the Persian Gulf. To reconstruct the campaign in Mesopotamia/Iraq after the reverses of 1915-16, the Indian Army demanded non-combatants for dock-work, construction labor and medical and transport services. This chapter explores the Government of India’s anxious deliberations about the choice of legal form in which to meet this demand. The sending of labor for military work overseas had to be distanced conceptually from the stigmatized system of indentured labor migration. There was a danger of disrupting those labor networks across India and around the Bay of Bengal which maintained the supply of material goods for the war. Non-combatant recruitment took the war into new sites and spaces. Regimes of labor servitude were tapped but some form of emancipation had to be promised. The chapter focusses on seven jail- recruited Indian Labor and Porter Corps to explore the work regime in Mesopotamia. Labor units often insisted on fixed engagements rather than ‘duration of war’ agreements, but had to struggle for exit at the conclusion of their contract. After the Armistice, Britain still needed Indian labor and troops in Mesopotamia but sought to prevent the emergence of a settler population.
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Oldroyd, Keith G., e Colin Berry. "Invasive functional evaluation". In ESC CardioMed, a cura di William Wijns, 1354–60. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198784906.003.0333.
Testo completoAbstract (sommario):
Based on an understanding of how a stenosis impacts the ability of a coronary artery to deliver adequate myocardial blood flow, coupled with the results of the DEFER, FAME, and FAME 2 studies, fractional flow reserve (FFR) has become the most widely used and the only guideline-recommended method for the invasive functional evaluation of patients with stable ischaemic heart disease. The absolute value of FFR predicts prognosis and when treatment decisions are made or modified in response to the FFR value, clinical outcomes are improved. Major adverse cardiovascular event rates related to lesions deferred for revascularization on the basis of non-ischaemic FFR results are low. When compared to FFR, resting (non-hyperaemic) indices of physiological stenosis severity such as resting Pd/Pa or instantaneous wave-free ratio are associated with misclassification of 20% of lesions using binary cut-off values and 10% of lesions when hybrid strategies are used. Nevertheless, in low-risk patient populations, randomized clinical trials comparing instantaneous wave-free ratio versus FFR-guided management have shown non-inferiority. A comprehensive invasive assessment of patients with stable ischaemic heart disease requires an evaluation of microvascular dysfunction most commonly obtained by measuring the index of microcirculatory resistance. Patients with non-ischaemic FFR values but an elevated index of microcirculatory resistance have an increased incidence of adverse events.
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Erbel, Raimund. "Aortic sclerosis: therapy". In ESC CardioMed, a cura di Raimund Erbel, 2583–89. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198784906.003.0613.
Testo completoAbstract (sommario):
Aortic sclerosis is a very common disease and is related to the atherosclerotic process which can start in young adulthood. The loss of compliance of the aortic ‘Windkessel’ is a major drawback of the disease, leading to enhanced blood pressure amplitude—elevated pulse pressure—due to a higher systolic and a lower diastolic blood pressure. The pressure pulse wave augmentation index and the pulse wave velocity increase. Ultrasound is able to visualize only limited aortic segments, whereas computed tomography and magnetic resonance imaging are the best tools to detect and quantify aortic atheromas. Nevertheless, transoesophageal echocardiography can image the descending thoracic aorta down to the coeliac trunk. An aortic atheroma, particularly one greater than 4 mm in size in the aortic arch, indicates an increased risk of stroke and other cardiovascular events. A grading is helpful. Plaque rupture is quite frequent and often found in multiple segments of the aorta indicating an increased risk of cholesterol emboli due to the wash-out of debris with or without thrombotic material. Free-floating structures, possible remnants of fibrous cap, are found as well as mobile thrombi. Calcification of the thoracic aorta is often found when coronary artery calcification is present, but may be present when coronary artery calcification is absent. Risk prediction of events is, however, not improved. Therapy for aortic sclerosis is based on common and recent guidelines for prevention and treatment of risk factors. Endovascular or surgical interventions are limited to rare situation in which blood flow is not preserved.
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Lynch, Bryan E. "The ReliantHeart aVAD©". In Mechanical Circulatory Support, 103–9. Oxford University Press, 2019. http://dx.doi.org/10.1093/med/9780190909291.003.0015.
Testo completoAbstract (sommario):
The ReliantHeart aVAD© is a new intraventricular axial flow pump with pumping components that fit within the inflow cannula of the ventricular assist device (VAD). The aVAD© is an improvement over its predecessor, the extra-ventricular HeartAssist5 (HA5)™. The pumping components, inflow guide vane, impeller, and diffuser of the aVAD© are identical to those in the HA5, which in turn were derived from the original collaboration between Baylor College of Medicine and NASA. The current device provides excellent physiologic support for patients in end-stage heart failure and provides advanced ultrasonic flow measurements and performance data for wireless remote monitoring. In 2011 and 2012, the aVAD© was used successfully in calf studies as an artificial heart, with each ventricle being replaced by a modified HA5 VAD©. The two predecessor aVADs© were placed vertically, side by side, which provided a more compact total artificial heart with formable outflow graft protectors directed to the aorta and pulmonary artery. An ultrasonic flow probe accurately measures flow under all conditions, even in implants in place for years. The probe indicates flow in the range of –4 to +10 L/min with >95% accuracy. The probe can determine the relative contributions of the LVAD and native heart to adequate blood flow. The aVAD© meets the safety standards of the European Union and is sold in Europe. The aVAD is not yet available in the United States but is being tested under an FDA investigational device exemption.
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"39 Effect of Menopausal Status and Hormone Replacement on Therapy Resistance Indices and Blood Flow Velocities in Breast Tumors". In Color Doppler Sonography in Gynecology and Obstetrics, a cura di Werner O. Schmidt e Asim Kurjak. Stuttgart: Georg Thieme Verlag, 2005. http://dx.doi.org/10.1055/b-0034-87352.
Testo completoAtti di convegni sul tema "Blood flows indices"
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Saldaña, Charles Huamani, William Bayona Pancorbo, Víctor Oré Montalvo, Carlos Pérez Alviz, Juan Carlos Acuña Mamani, Golda Córdova Heredia, Paulina Damián-Saavedra et al. "Preliminary correlation between blood viscosity and pulsatility index in healthy population resident at high altitude (Cusco 3300 masl)". In XIII Congresso Paulista de Neurologia. Zeppelini Editorial e Comunicação, 2021. http://dx.doi.org/10.5327/1516-3180.454.
Testo completoAbstract (sommario):
Background: Viscosity affects flows by increasing resistance to movement, therefore, blood viscosity (BV) could modify the pulsatility index (PI). Objectives: To determine the correlation between BV and PI. Design and setting: A cross-sectional study was conducted in clinically healthy young adults residing in Cusco (a city located at 3399 masl). Methods: A venous blood sample was taken to determine their BV levels, and a transcranial Doppler of right middle cerebral artery (R-MCA) was performed, with which the min, maximum and mean flow velocity (MFV), resistance and pulsatility indices (PI) were obtained. The BV levels were measured in centipoises (cP) using acone-plate viscometer at 40RPM. We present medians with interquartile ranges (IQR), the correlation was evaluated using the Spearman test. Results: 42 participants were included, 25 women (60%), the mean age was 26.2±5.5 years. The median of BV was 5.08cP [IQR: 4.55-5.77cP], the MFV was 56 m/s [IQR: 49- 61 m/s], and the PI was 0.94 [0.85-1.02]. BV was positively correlated with PI (r:0.38, p=0.045) and negatively with MFV (r: -0.37, p=0.011) Conclusions: The increase in blood viscosity has a small but significant impact on cerebral vascular resistance (PI) and its fluxes (MFV) in clinically healthy and young people. This could have a role in the pathogenesis of cerebral infarction in the elderly. The results presented here are preliminary and we intend to gather more data and increasing our number of participants.
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Hao, Zhili. "Relations of Radial Vibration of the Arterial Wall to Pulsatile Parameters in Blood Flow for Extraction of Arterial Indices". In ASME 2022 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/imece2022-95084.
Testo completoAbstract (sommario):
Abstract In light of the utility of radial vibration of the arterial wall for clinical values, this paper presents a theoretical study on the relations of radial vibration of the arterial wall to pulsatile parameters in blood flow. Pulse wave propagation in an artery is formulated as a combination of the governing equations of blood flow and the arterial wall and no-slip conditions at the blood-wall interface. A free wave propagation analysis is conducted on the problem to obtain the wave velocity and the theoretical expressions for blood flow rate and arterial radial displacement in terms of pulsatile pressure. With the harmonics of a pulse signal, mathematical relations of radial vibration of the arterial wall to pulsatile parameters in blood flow are derived under two conditions: without and with wave reflection. These mathematical relations identify the assumptions for the simplified relations employed in the utility of radial vibration of the arterial wall for extraction of arterial indices. With the arterial wall treated as a unit-mass vibration system, these simplified relations are utilized for extraction of arterial indices from radial vibration of the arterial wall. Some other aspects of radial vibration of the arterial wall are further discussed.
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Ito, Kenichi, Yuki Kourakata e Yu Hotta. "Muscle fatigue detection during dynamic contraction under blood flow restriction: Improvement of detection sensitivity using multivariable fatigue indices". In 2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC). IEEE, 2015. http://dx.doi.org/10.1109/embc.2015.7319778.
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Das, Ashish, William M. Gottliebson, Janaka Wansapura e Rupak K. Banerjee. "Development of a Methodology for Direct Utilization of Phase-Contrast MRI in Hemodynamic Computations". In ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53959.
Testo completoAbstract (sommario):
Development of non-invasive diagnostic indices often requires accurate blood-flow calculation using physiologically realistic velocity profiles as boundary conditions. In this research, a methodology is being developed and validated that can directly use phase-contrast MR imaging (PC-MRI) based velocity measurement to perform blood-flow computation with patient-specific geometry. Using this methodology, the pressure drop can also be calculated non-invasively. Although the main focus of our research has been pulmonary insufficiency (PI) in tetralogy patients, our method can be employed in many other pathophysiologies. As a pilot study, the methodology is tested using a simple model of blood-flow through a straight artery of uniform cross-section.
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Retarekar, Rohini, Manasi Ramachandran e Raghavan L. Madhavan. "Correlation Among Hemodynamic and Morphological Metrics of Intracranial Aneurysms". In ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80708.
Testo completoAbstract (sommario):
There is increasing interest in assessing metrics of blood flow characteristics as prognostic indicators of rupture risk in intracranial aneurysms. Aneurysmal hemodynamics may be and has been quantified in the literature by numerous indices (about 18, to the best of our knowledge) each capturing some characteristic of flow. But are all these indices capturing unique characteristics of flow or are many of them redundant? And are they mainly proxies for basic morphological characteristics? Answering this question and identifying the indices that capture unique aspects of flow has practical implications to prospective studies designed to test the hemodynamics-rupture correlation. Lesser the number of indices, lesser will be the required sample sizes for sufficient statistical power. Alternatively, greater the number of indices, greater the likelihood that such studies will descend into an exercise in data mining. Further, understanding how these indices relate among themselves and to morphology can help us better reconcile findings from independent studies. The objectives of this study were to first document and categorize all reported indices in the literature and use a population of unruptured intracranial aneurysms to understand correlations among them and with morphological indices.
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Chaudhari, Krunal, e Hardikkumar Patel. "Hemodynamics Numerical Simulation of Stenosis Bifurcation". In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51072.
Testo completoAbstract (sommario):
The main purpose of this research is to analyze blood flow in various scenarios such as 20%, 50% and 80% blockage in blood vessel due to aortic atherosclerosis. Valuable Information for clinical diagnosis of cardiovascular diseases can be obtained by analyzing the behavior of blood flow and its variations. An idealized numerical model of the human bifurcated aorta is created then simulations of steady blood flow were performed on this model and various parameters have been considered. The model parameters include the blood flow velocity, pressure, wall shear stress (WSS) of vessels, constant blood density and constant viscosity. The data computed from software indicates behavior of blood flow according to changes in physical properties of blood vessel. These results are mostly similar to physiological and pathological results of vessels observed in clinical practice. This study will eventually help to find the Fluid Structure Interaction (FSI) of blood flow and blood vessel which will be bring a favorable change in cardiovascular diseases treatments.
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Bhavsar, Sonya S., William B. Moskowitz e Amy L. Throckmorton. "Mechanical Assistance for the Fontan Circulation Using an Intravascular Axial Flow Blood Pump". In ASME 2010 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2010. http://dx.doi.org/10.1115/sbc2010-19154.
Testo completoAbstract (sommario):
Research indicates that an afterload reducing agent improves ventricular-vascular interactions and Fontan hemodynamics [1]. Few such therapeutic alternatives exist for the failing Fontan patient beyond conventional pharmacologic therapy. To address this need for therapeutic options, we are developing an intravascular, magnetically levitated axial flow blood pump to support the total cavopulmonary connection (TCPC) of a failing Fontan in adolescent and adult patients [1,2]. Our pump is designed to provide mechanical pressure augmentation of blood flow from the inferior vena cava (IVC) to the lungs, thus improving systemic venous pressure and increasing ventricular filling.
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Shida, Shuya, Hiroyuki Kosukegawa e Makoto Ohta. "Development of a Methodology for Adaptation of Refractive Index Under Controlling Kinematic Viscosity for PIV". In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-64388.
Testo completoAbstract (sommario):
Blood vessel diseases such as ischemic cardiac disease or cerebral aneurysm are life-threatening disorders and as large a cause of death as cancer in many countries. The rupture of a cerebral aneurysm usually causes subarachnoidal hemorrhage the mortality of which is very high. Previous studies have proved that the genesis and growth of aneurysm are related to hemodynamics. Especially, in endovascular therapy for cerebral aneurysms using medical devices such as coils or stents, hemodynamics in an aneurysm are related to thrombosis formation in the aneurysm and to its repair. In vascular research using a biomodel (blood vessel phantom with mechanical properties similar to a human artery) for treating cerebral aneurysm, the working fluid, termed Blood-Mimicking Fluid (BMF), should mimic human blood with respect to viscosity so as to obtain realistic blood flow modeling in in vitro measurements. Moreover, refractive indices of BMF must be adjusted to fit biomodel materials because the materials used for Particle Image Velocimetry, one of the best tools for measurement of flow, have various refractive indices. For simultaneous adjustment of the two parameters, i.e. kinematic viscosity and refractive index, an aqueous mixture of glycerol and sodium iodide has been used in previous research. In this paper, we develop a systematic way to precisely find the two targeted parameters of BMF by showing the measurement values of the refractive index and the viscosity of the two aqueous solutions. The refractive index to light of fluorescent was measured with a critical angle refractometer while temperature of sample was also measured. And a vibration-type viscometer was used to obtain the dynamic viscosity under the same condition as refractive index measurement. These measurements were carried out at room temperature and pressure, respectively. As a result of detailed measurements at various proportions, refractive indices of the aqueous solution of glycerol (Gly. aq.) increase monotonically. On the one hand, the kinematic viscosity of Gly. aq. increases very slightly with its proportion and that of the aqueous solution of sodium iodide (NaI aq.) exhibits unique behavior. The results of combining Gly. aq. and NaI aq. indicate that the mixture has a wide range of kinematic viscosity, including the value of blood (around 3.8 mm2/s), at the targeted refractive index. In conclusion, this mixing method is useful for BMF preparation with the adjustment of refractive index and kinematic viscosity.
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Kim, Soyoon, Kyoungchul Ro e Hong Sun Ryou. "Numerical Investigation for the Effect of Blood Flow Rate and Asymmetric Bifurcation Angle on the Anterior Circulation Aneurysm Formation". In ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-19009.
Testo completoAbstract (sommario):
Most of aneurysms in the cranial cavity occur at the bifurcation of anterior circulation system. A cerebral aneurysm is easily ruptured, and it is fatal for most patients. Generally it is known that aneurysm occurs when arterial wall is deformed by high pressure or high wall shear stress (WSS). A blood flow pattern and the geometry and the blood vessel are important factors for aneurysm formation and the location. The transient interaction between blood flow and the arterial wall affects for simulating deformation of the blood vessel. Thus, numerical analysis is performed for various bifurcation angles and flow rate ratio in bifurcation artery with different diameters to predict the location of aneurysm by hemodynamic characteristics of blood flow. A bifurcation angle between the internal carotid artery and the anterior cerebral artery (ACA) increased, a region of high pressure moved to the bifurcated artery with larger bifurcation angle when ratio of blood flow rate is constant case. When the ratio of blood flow increased, the region of high wall shear stress moved to the side of large flow rate ratio. Our results showed that the high WSS or high pressure region occur at the location of aneurysm as mentioned in the clinical research. Thus, this indicates that the geometry of blood vessel and blood flow rate affect the location of the anterior circulation aneurysm.
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Otani, Tomohiro, Satoshi Ii, Toshiyuki Fujinaka, Masayuki Hirata, Junko Kuroda, Katsuhiko Shibano e Shigeo Wada. "Development of a Virtual Coil Model for Blood Flow Simulation in Coil-Embolized Aneurysms". In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-64435.
Testo completoAbstract (sommario):
Hemodynamics is considered to be one of the indices to evaluate the effects of the treatment by coil embolization for cerebral aneurysms. For the sake of detailed analysis of hemodynamics in coil-embolized aneurysms, we develop a virtual coil model based on the mechanical theory that the coil deforms toward minimizing the elastic energy, and represent a realistic configuration of the embolized coils in the aneurysm by the insertion simulation. Then, the blood flow analysis is done by solving the N.S. and continuity equations numerically with the finite volume method using polyhedral mesh. The coil insertion simulation demonstrated that almost uniform distribution of the coil in the aneurysm was achieved at over 10% packing density of the coil. The blood flow analysis using the virtual coil model showed that the flow momentum inside the aneurysm was reduced to less than 10% by coil embolization with a packing density over 20%. In comparison to the simulation results using a porous media model for the embolized coil, there was no significant difference in the reduction ratio of the flow momentum in the aneurysm by coil embolization. However, local flow dynamics evaluated by the flow vorticity was different in the virtual coil model and the porous media model, in particular at the neck region of the aneurysm.