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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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Patent
17 Feb 1984
TL;DR: In this paper, a continuous long-term non-invasive measurement of the pressure of a pulsatile fluid flowing through a flexible tube, particularly human arterial blood flow, is disclosed.
Abstract: Apparatus and related methods for continuous long-term non-invasive measurement of the pressure of a pulsatile fluid flowing through a flexible tube, particularly human arterial blood flow, is disclosed. Specifically, the apparatus provides a continuous calibrated pressure measurement by first undertaking a "calibration" phase comprised of determining the pressure at various pre-defined conditions of flow and, in reponse thereto, ascertaining the values of a plurality of coefficients each of which is associated with a corresponding term in a pre-defined function that characterizes fluid pressure in relation to pulsatile displacement of the wall of the tube; and second, undertaking a "continuous monitoring" phase comprised of determining each subsequently occurring pressure value as the pre-defined function of each corresponding pulsatile wall displacement value, and re-initiating the calibration phase at the expiration of pre-defined time intervals which adaptively change based upon current and prior results. Methods, which are particularly useful in conjunction with the disclosed apparatus, for ascertaining systolic and diastolic arterial blood pressure values are also disclosed.

58 citations

Journal ArticleDOI
TL;DR: If the extent of sensor deformation correlates with the intensity of flow-mediated endothelial signaling, then the results suggest possible mechanisms by which ECs distinguish among steady, non-reversing pulsatile, and oscillatory shear stress.

58 citations

Journal ArticleDOI
TL;DR: In this review, recent patents on pulsatile drug delivery of oral dosage forms are summarized and discussed.
Abstract: Pulsatile drug delivery aims to release drugs on a programmed pattern i.e.: at appropriate time and/or at appropriate site of action. Currently, it is gaining increasing attention as it offers a more sophisticated approach to the traditional sustained drug delivery i.e: a constant amount of drug released per unit time or constant blood levels. Technically, pulsatile drug delivery systems administered via the oral route could be divided into two distinct types, the time controlled delivery systems and the site-specific delivery systems. The simplest pulsatile formulation is a two layer press coated tablet consisted of polymers with different dissolution rates. Homogenicity of the coated barrier is mandatory in order to assure the predictability of the lag time. The disadvantage of such formulation is that the rupture time cannot be always adequately manipulated as it is strongly correlated with the physicochemical properties of the polymer. Gastric retentive systems, systems where the drug is released following a programmed lag phase, chronopharmaceutical drug delivery systems matching human circadian rhythms, multiunit or multilayer systems with various combinations of immediate and sustained-release preparation, are all classified under pulsatile drug delivery systems. On the other hand, site-controlled release is usually controlled by factors such as the pH of the target site, the enzymes present in the intestinal tract and the transit time/pressure of various parts of the intestine. In this review, recent patents on pulsatile drug delivery of oral dosage forms are summarized and discussed.

58 citations

Journal ArticleDOI
TL;DR: The main structures observed in steady flow, such as vortices in the distal artery and helical flow in the graft, were also seen during the pulsatile cycle, however, the secondary flow components inthe graft were more pronounced in pulsatile flow particularly during deceleration of the flow waveform.
Abstract: Flow structures were visualized in transparent polyurethane models of proximal side-to-end vascular anastomoses, using planar illumination of suspended tracer particles. Both the effects of geometry and flow division were determined under steady and pulsatile flow conditions, for anastomosis angles of 15, 30, and 45 degrees. The flow patterns were highly three-dimensional and were characterized by a series of vortices in the fully occluded distal artery and two helical vortices aligned with the axis of the graft. In steady flow, above a critical Reynolds number, the flow changed from a laminar regime to one displaying time-dependent behavior. In particular, significant fluctuating velocity components were observed in the distal artery and particles were shed periodically from the occluded artery into the graft. Pairs of asymmetric flow patterns were also observed in the graft, before the onset of the time-dependent flow regime. The critical Reynolds number ranged from 427 to 473 and appeared to be independent of anastomosis angle. The presence of a patent distal artery had a significant effect on the overall flow pattern and led to the formation of a large recirculation region at the toe of the anastomosis. The main structures observed in steady flow, such as vortices in the distal artery and helical flow in the graft, were also seen during the pulsatile cycle. However, the secondary flow components in the graft were more pronounced in pulsatile flow particularly during deceleration of the flow waveform. At higher mean Reynolds numbers, there was also a greater mixing between fluid in the occluded arterial section and that in the graft.

58 citations

Journal ArticleDOI
TL;DR: Hemodynamic load provoked by isometric exercise strongly predicts LVMI in hypertension, suggesting that provoked testing captures important arterial properties that are not apparent at rest and is advantageous to assess dynamic arterial load in hypertension.
Abstract: Although resting hemodynamic load has been extensively investigated as a determinant of left ventricular (LV) hypertrophy, little is known about the relationship between provoked hemodynamic load a...

58 citations


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