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Pulsatile flow

About: Pulsatile flow is a research topic. Over the lifetime, 6278 publications have been published within this topic receiving 149638 citations.


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TL;DR: The increased characteristic input impedance in these heart failure patients suggests that the human aorta is stiffer in heart failure, and the larger oscillations in the impedance spectrum indicate an increase in pressure and flow wave reflections.
Abstract: The input impedance of the systemic circulation was calculated from recordings of pulsatile pressure and flow in the ascending aorta of 20 patients. Ten patients had clinical and hemodynamic evidence of heart failure. The other 10 subjects had no clinical evidence of heart failure and were used as a control group. In the heart failure patients, both input resistance and characteristic impedance (index of aortic distensibility) were significantly increased compared to pressure- and age-matched control subjects. Oscillations of impedance moduli, represented by the difference between maximum and minimum moduli, were also significantly increased in the heart failure patients compared with the control subjects. The increased characteristic input impedance in these heart failure patients suggests that the human aorta is stiffer in heart failure, and the larger oscillations in the impedance spectrum indicate an increase in pressure and flow wave reflections. From reflected wave theory in elastic tubes, reflected pressure waves add to the amplitude of incident pressure waves at the entrance of the system, whereas reflected flow waves subtract from the magnitude of the forward flow. Thus, changes in aortic distensibility could have an important influence on the pulsatile function of the failing left ventricle.

151 citations

Journal ArticleDOI
TL;DR: A lattice Boltzmann method for simulating the viscous flow in large distensible blood vessels is presented by introducing a boundary condition for elastic and moving boundaries, and the numerical results for steady flow agree with the analytical prediction to very high accuracy.
Abstract: A lattice Boltzmann method for simulating the viscous flow in large distensible blood vessels is presented by introducing a boundary condition for elastic and moving boundaries. The mass conservation for the boundary condition is tested in detail. The viscous flow in elastic vessels is simulated with a pressure-radius relationship similar to that of the Pulmonary blood vessels. The numerical results for steady flow agree with the analytical prediction to very high accuracy, and the simulation results for pulsatile flow are comparable with those of the aortic flows observed experimentally. The model is expected to find many applications for studying blood flows in large distensible arteries, especially in those suffering from atherosclerosis. stenosis. aneurysm, etc.

150 citations

Journal ArticleDOI
TL;DR: The linear relationships between parameters of the recorded curves and the mean transit times indicate that the effect of rate of flow, over a range from resting values to four to six times above resting values, has almost no influence on the dispersion, suggesting that the flow characteristics are essentially unchanged over this range.
Abstract: 1. Indicator dilution curves (concentration versus time) were recorded from the femoral and dorsalis pedis arteries of normal men after injections of indocyanine green into the superior vena cava or thoracic aorta. A four-parameter mathematical model, the lagged normal density curve, adequately described the form of the portion of these curves representing indicator passing by the sampling site for the first time. 2. The curves were observed to be of constant shape, the spread of the curve being approximately linearly related to the mean transit time t. The spread was dependent on the injection site; dispersion was shown to be greatest in the central circulation, less in the aorta, and still less in the arteries of the leg. For the latter segment, the mean transit time t. The spread was dependent 0.3 t, the square root of the variance was 0.18 t, and the parameters of the lagged normal density curve, σ and τ, were 0.09 t and 0.16 t, respectively. 3. The linear relationships between parameters of the recorded curves and the mean transit times indicate that the effect of rate of flow, over a range from resting values to four to six times above resting values, has almost no influence on the dispersion. This suggests that the flow characteristics are essentially unchanged over this range. Such linear relationships always occur with laminar flow but cannot prove its existence because turbulent flow can also produce this result. The similarity of the linear relationships at low flow rates to those at high flow rates, where turbulence almost certainly is present, suggests that arterial flow is usually turbulent. Turbulence may be expected at relatively low flow rates in nonhomogeneous fluids driven by a pulsatile head of pressure through elastic, branched, tapering, curved tubes.

150 citations

Journal ArticleDOI
TL;DR: Pressure and flow wave contour and impedance results were interpreted with the aid of a multibranched model of the systemic arterial tree, whose parameters could be manipulated to simulate different physiological and pathological conditions.
Abstract: This study seeks to explain mechanisms responsible for the contour of pressure and flow waves and the pattern of vascular impedance in human systemic arteries. Pulsatile pressure and flow were recorded from the ascending aorta of seven patients undergoing open heart surgery and from the ascending aorta and other arteries of 17 patients at diagnostic catheterization. Ascending aortic pressure/flow relationships in the seven surgical patients were expressed as input impedance to the systemic circulation. Pressure and flow wave contour and impedance results were interpreted with the aid of a multibranched model of the systemic arterial tree, whose parameters could be manipulated to simulate different physiological and pathological conditions. Our data and data previously published on pressure and flow waves and their relationship in human subjects could be explained on the basis of two reflecting sites in the systemic circulation-one representing the resultant of all arterial terminations in the upper part of the body, and the other, some 1.5 times further away, the resultant of all arterial terminations in the lower body. The concept of the arterial system as an asymmetric T tube with two discrete ends has been advanced previously to explain the main features of pressure and flow waves and their relationship in different experimental animals. This concept appears equally applicable to human subjects. Circ Res 46: 363-372, 1980

149 citations

Journal ArticleDOI
01 Aug 1986-Diabetes
TL;DR: By reducing total hormone delivery by up to 40%, but given in a pulsatile fashion, insulin is equally potent in controlling HGP as continuous insulin administration, accompanied by an equipotent effect on glucose utilization.
Abstract: To evaluate the role of pulsatile insulin administration, hepatic glucose production (HGP) and utilization were studied in type I diabetic patients in the fasting state and during a euglycemic insulin (1 mU · kg −1 · min −1 i.v.) clamp with continuous and pulsatile insulin administration. In the latter study, insulin was infused at twice the continuous rate with 3-min-on/7-min-off intervals, thereby reducing total insulin delivery by 40%. The restraining effect of pulsatile insulin on basal HGP (1.91 ± 0.35 mg · kg −1 · min −1 ) was equipotent to continuous insulin exposure (1.80 ± 0.17 mg · kg −1 min −1 ). During the insulin-clamp studies, HGP was equally suppressed by pulsed (0.62 ± 0.12 mg · kg −1 min −1 ) as by continuous insulin infusion (0.63 ± 0.12 mg · kg −1 · min −1 ). Insulin-stimulated glucose utilization was not significantly altered in either study (2.55 ± 0.27 vs. 2.92 ± 0.23 mg · kg −1 min −1 ). When in further studies the total insulin dose given during the pulsatile study was infused continuously (0.6 mU · kg −1 · min −1 ), HGP in the basal state and residual HGP during the insulin-clamp study were 25–30% higher than in the pulsatile experiments, whereas glucose utilization was not significantly different. In conclusion, by reducing total hormone delivery by up to 40%, but given in a pulsatile fashion, insulin is equally potent in controlling HGP as continuous insulin administration. This greater efficacy of pulsatile exposure in suppressing HGP is accompanied by an equipotent effect on glucose utilization. Application of pulsatile insulin substitution in intravenous-pump users may reduce systemic hyperinsulinemia and, in the long run, insulin resistance by reversing downregulation of insulin receptors.

148 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023274
2022641
2021170
2020181
2019171
2018189