Vascular impedance

2011 ◽  
pp. 287-324
Keyword(s):  
Vascular Impedance

A keystone solution for major head and neck reconstructions

2019 ◽  
Vol 2 (2) ◽  
pp. 79-83
Author(s):  
Felix Behan
Keyword(s):  
Head And Neck ◽  
The Elderly ◽  
Microvascular Surgery ◽  
Island Flap ◽  
Aesthetic Outcome ◽  
Vascular Impedance ◽  
Supplementary Video

This ‘How to do it’ lists a range of cases, demonstrated by supplementary video discussion, that explain the refinements of the keystone perforator island flap (KPIF) technique applied to specific sites of the head and neck, with a focus on the elderly. When the P A C E acronym is applied (pain-free, aesthetic outcome, minimal complications, economical) the KPIF technique is a respectable alternative to microvascular surgery, particularly in the elderly, with minimal returns to theatre for vascular impedance problems which are not infrequent in microvascular reconstructions.  

Color doppler ultrasonography of soft-tissue masses

1998 ◽  
Vol 39 (4) ◽  
pp. 421-426 ◽  
Author(s):  
R. Lagalla ◽  
A. Iovane ◽  
G. Caruso ◽  
M. Lo Bello ◽  
L. E. Derchi
Keyword(s):  
Soft Tissue ◽  
Doppler Ultrasonography ◽  
Color Doppler ◽  
Soft Tissue Tumors ◽  
Color Doppler Ultrasonography ◽  
Tissue Mass ◽  
Vascular Impedance ◽  
The Us ◽  
Soft Tissue Masses ◽  
Malignant Lesions

Purpose: To evaluate the capability of color Doppler ultrasonography to differentiate between benign and malignant soft-tissue tumors. Material and Methods: We reviewed the ultrasonographic (US) and color Doppler (CD) findings in 46 consecutive patients with a palpable periskeletal mass. The presence of 3 or more vascular hila and of tortuous and irregular internal vessels within the lesions was considered an indication of malignancy. The CD diagnosis was compared with that obtained at US alone. Results: The sensitivity and specificity of CD were respectively 85% and 92%; these values were higher than those obtained at US alone, respectively 75% and 50%. Arteriovenous malformations presented as lesions with large internal vessels that had low vascular impedance and were easily diagnosed. The waveform patterns within solid tumors were not specific. Conclusion: At present, US is commonly employed to confirm the presence of a suspected soft-tissue mass, to locate it accurately, and to indicate its nature. CD findings enhance the role of the US technique in such lesions. The combined use of US and CD can allow the differentiation of benign from malignant lesions, and thus provide a better basis for treatment.

Abstract 3077: Cross-Sectional Associations of Arterial Stiffness Measures and Ankle-Brachial Index: The Multi-Ethnic Study of Atherosclerosis (MESA)

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
John T Wilkins ◽  
Mary M McDermott ◽  
Kiang Liu ◽  
Cheeling Chan ◽  
Michael Criqui ◽  
...  
Keyword(s):  
Arterial Stiffness ◽  
Mechanical Characteristics ◽  
Pulse Wave ◽  
Ankle Brachial Index ◽  
Arterial Disease ◽  
Cross Sectional ◽  
Men And Women ◽  
Independent Variables ◽  
Vascular Impedance ◽  
Peripheral Arterial

The association between tonometry-derived measures of arterial stiffness and peripheral arterial disease (PAD) is unclear. Using baseline data from 2847 female and 2614 male participants of the NHLBI-funded MESA study, we conducted linear regression analyses adjusted for age, demographics and risk factors. Ankle-brachial index (ABI) was the dependent variable and measures of large (C1) and small artery elasticity (C2) and total vascular impedance (TVI), all measured from radial artery tonometry, were the independent variables in separate models. In men and women, lower C1 and C2 values were associated with lower ABI. Higher TVI was associated with lower ABI in men and women [P<0.001]. Significant trends for C1, C2 and TVI were observed across clinical strata of ABI (Table ). In pairwise analyses, compared with participants with a normal ABI (1.1 to <1.3), those with ABI <1.1 tended to have significantly lower C2. Additionally, women with high ABI (1.3–1.5) tended to have significantly higher C2 values. Pairwise comparisons of lower and higher ABI groups compared with normal groups did not yield consistent findings for C1. Significantly higher TVI levels with lower ABI group were noted mostly in women (Table ). We observed a continuum of arterial mechanical characteristics across clinical ABI values, indicating that measures of arterial stiffness are significantly associated with ABI and severity of PAD. These results suggest that changes in C2 occur in patients with advanced lower extremity large-vessel atherosclerotic disease. Of note, female participants with high ABI between 1.3–1.5 had a significantly higher C2, arguing against the accepted “non-compressible” or “calcified arterial disease” explanation for high ABI in women. Associations Between ABI and Pulse Wave Analysis Measurements when adjusted for age, cigarette smoking, diabetes, hypertension, and creatinine level

Fetal cerebral vascular impedance is abnormal in left congenital diaphragmatic hernia

2020 ◽  
Author(s):  
Katherine A. Kosiv ◽  
Anita Moon‐Grady ◽  
Whitnee Hogan ◽  
Roberta Keller ◽  
Rebecca Rapoport ◽  
...  
Keyword(s):  
Congenital Diaphragmatic Hernia ◽  
Diaphragmatic Hernia ◽  
Vascular Impedance ◽  
Cerebral Vascular

Carotid sinus control of pulsatile hemodynamics in halothane-anesthetized dogs

1980 ◽  
Vol 238 (3) ◽  
pp. H294-H299
Author(s):  
R. H. Cox ◽  
R. J. Bagshaw
Keyword(s):  
Arterial Pressure ◽  
Carotid Sinus ◽  
Open Loop ◽  
Hydraulic Power ◽  
Set Point ◽  
Hemodynamic Variables ◽  
Vascular Impedance ◽  
Mean Pressure ◽  
Anesthetized Dogs ◽  
Sinus Pressure

The open-loop characteristics of the carotid sinus baroreceptor reflex control of pulsatile arterial pressure-flow relations were studied in halothane-anesthetized dogs. Pressures and flows were measured in the ascending aorta, the celiac, mesenteric, renal, and iliac arteries and were used to compute values of regional vascular impedance and hydraulic power. The carotid sinuses were bilaterally isolated and perfused under conditions of controlled mean pressure with a constant sinusoidal component. Measurements were made with the vagi intact and after bilateral vagotomy. Maximum values of open-loop gain averaged -0.78 +/- 0.08 before and -1.42 +/- 0.20 after vagotomy. Vagotomy produced significant increases in the variation of all hemodynamic variables with carotid sinus pressure that were nonuniformly affected in the various regional vascular beds. Aortic and regional vascular impedance showed significant variations with carotid sinus pressure that were augmented by vagotomy. Aortic impedance exhibited a minimum at the normal set point. These results indicate that a) carotid sinus baroreflexes are well preserved with halothane anesthesia, b) thoracic baroreceptor-mediated reflexes exert significant hemodynamic effects on systemic hemodynamics around normal set point values of arterial pressure, c) systemic baroreceptors exert control over large as well as small vessel properties, and d) the baroreceptor-mediated reflexes produce significant influences on hydraulic power and its components.

Vascular impedance analysis in dog lung with detailed morphometric and elasticity data

1994 ◽  
Vol 77 (2) ◽  
pp. 706-717 ◽  
Author(s):  
R. Z. Gan ◽  
R. T. Yen
Keyword(s):  
Pulsatile Flow ◽  
Input Impedance ◽  
Characteristic Impedance ◽  
Main Pulmonary Artery ◽  
Impedance Analysis ◽  
Elastic Tube ◽  
Vascular Impedance ◽  
Mean Pressure ◽  
Vascular Obstruction ◽  
Arteries And Veins

On the basis of experimentally measured morphometric and elasticity data and model-derived mean pressure-flow conditions, we attempt a theoretical modeling of pulsatile flow in the whole lung. In the model we use the "elastic tube" for arteries and veins, and the vascular impedance in arteries and veins follows Womersley's theory and electric analogue. We employ the “sheet-flow” theory to describe the flow in the capillaries and to obtain the microvascular impedance matrix. The characteristic impedance of each order along the vascular tree, the input impedance at the capillary entrance and exit, and the pulmonary arterial input impedance at the main pulmonary artery are computed under certain physiological conditions. Using the pulsatile flow model, we investigate the effects of arterial vascular obstruction on pulmonary vascular impedance. The model-derived data are compared with the available experimental results in the literature.

Effects of norepinephrine on mechanics of arteries in vitro

1976 ◽  
Vol 231 (2) ◽  
pp. 420-425 ◽  
Author(s):  
RH Cox
Keyword(s):  
Smooth Muscle ◽  
Pressure Dependence ◽  
Muscle Activation ◽  
Characteristic Impedance ◽  
Transmural Pressure ◽  
External Diameter ◽  
Vascular Impedance ◽  
Before And After ◽  
Tonic Level

The effects of smooth muscle activation on the pressure dependence of arterial wall characteristic impedance were studied with isolated segments of canine iliac and carotid arteries. Measurements of external diameter and transmural pressure were made before and after activation of the arterial smooth muscle (SM) by norepinephrine (NE) in concentrations of 0.5 and 5 mug/ml and used to compute values of characteristic impedance (Z0). In the absence of SM tone, values of Z0 for both arterial sites increased monotonically with transmural pressure. For the larger [NE], values of ZO exhibited a minimum at pressures of the order of 125 mmHg and increased for both larger and smaller values of pressure, For the smaller [NE], values of Z0 showed a similar pressure dependence but with a broader minimum. It is concluded that the previously demonstrated constancy of vascular impedance with changes in arterial pressure is at least the result of the presence of a tonic level of SM activation in conduit arteries.

Contrast-Free Blood Flow Velocity Profile Measurement With Ultrasound in Real-Time

2011 ◽  
Author(s):  
G. G. Koutsouridis ◽  
N. Bijnens ◽  
S. van Geldermalsen ◽  
P. J. Brands ◽  
F. N. van de Vosse ◽  
...  
Keyword(s):  
Blood Flow ◽  
Blood Velocity ◽  
Profile Measurement ◽  
Doppler Measurement ◽  
Non Invasive ◽  
Hemodynamic Variables ◽  
Vascular Impedance ◽  
Velocity Profile Measurement ◽  
Invasive Method ◽  
Flow Velocity Profile

In clinical practice, ultrasound is frequently used as a non-invasive method to estimate geometric properties of large arteries such as diameter and intima-media wall thickness and in a separate Doppler measurement hemodynamic variables such as blood velocity. For the purpose of deducing biomechanical parameters and hemodynamic variables that are related to the development of Cardiovascular Disease, such as compliance and vascular impedance, the assessment of only geometry and blood velocity is not sufficient. A simultaneous and non-invasive assessment of blood flow and blood pressure is required. This can only be obtained by an accurate and simultaneous measurement of the blood velocity distribution and wall motion, which is not feasible with the commonly used Doppler technique.

Towards Non-Invasive Pressure Assessment

2010 ◽  
Author(s):  
Nathalie Bijnens ◽  
Bart Beulen ◽  
Peter Brands ◽  
Marcel Rutten ◽  
Frans van de Vosse
Keyword(s):  
Wall Thickness ◽  
Vessel Wall ◽  
Biomechanical Properties ◽  
Vessel Diameter ◽  
Local Pressure ◽  
Vessel Wall Thickness ◽  
Non Invasive ◽  
Vascular Impedance ◽  
Vessel Wall Properties ◽  
Invasive Techniques

In clinical practice, ultrasound is frequently applied to non-invasively assess blood velocity, blood volume flow and blood vessel wall properties such as vessel wall thickness and vessel diameter waveforms. To convert these properties into relevant biomechanical properties that are related to cardiovascular disease (CVD), such as elastic modulus and compliance of the vessel wall, local pressure has to be assessed simultaneously with vessel wall thickness and vessel diameter waveforms. Additionally, accurate estimates of vascular impedance (transfer function between pressure and blood flow) can be a valuable tool for the estimation of the condition of the vessel, e.g., to diagnose stenosis. Studies of arterial impedance in humans, however, are hampered by the lack of reliable non-invasive techniques to simultaneously record pressure and flow locally as a function of time. Local pressure assessment together with flow has great potential for improving the ability to diagnose and monitor CVD.

Sex Differences in Right Ventricular-Vascular Coupling and Pulmonary Artery Impedance in Response to Chronic Hypoxia and Recovery

2012 ◽  
Author(s):  
Aiping Liu ◽  
Lian Tian ◽  
Diana M. Tabima ◽  
Naomi C. Chesler
Keyword(s):  
Pulmonary Artery ◽  
Chronic Hypoxia ◽  
Pulmonary Arteries ◽  
Pulmonary Artery Hypertension ◽  
Vascular Impedance ◽  
Female Predominance ◽  
Collagen Accumulation ◽  
Dominant Disease ◽  
Pulmonary Arterial

Pulmonary artery hypertension (PAH) is a female dominant disease (the female-to-male ratio is 4:1), characterized by small distal pulmonary arterial narrowing and large proximal arterial stiffening, which increase right ventricle (RV) afterload and ultimately lead to RV failure [1,2]. Our recent studies have shown that collagen accumulation induced by chronic hypoxia increases the stiffness of the large extralobar pulmonary arteries (PAs) [3], and affects pulmonary vascular impedance (PVZ) [4]. The role of collagen in the female predominance in developing PAH has not been explored to date.

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