Theory to predict shear stress on cells in turbulent blood flow
TL;DR: It is demonstrated that energy dissipation as opposed to bulk shear stress in laminar or turbulent blood flow dictates local mechanical environment of blood cells and platelets universally.
Abstract: Shear stress on blood cells and platelets transported in a turbulent flow dictates the fate and biological activity of these cells. We present a theoretical link between energy dissipation in turbulent flows to the shear stress that cells experience and show that for the case of physiological turbulent blood flow: (a) the Newtonian assumption is valid, (b) turbulent eddies are universal for the most complex of blood flow problems, and (c) shear stress distribution on turbulent blood flows is possibly universal. Further we resolve a long standing inconsistency in hemolysis between laminar and turbulent flow using the theoretical framework. This work demonstrates that energy dissipation as opposed to bulk shear stress in laminar or turbulent blood flow dictates local mechanical environment of blood cells and platelets universally.
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01 Jan 1994
TL;DR: In this paper, recent developments in three dimensional and unsteady turbulence boundary layer computations are discussed, including the physics of convention solidification interaction, the continental shelf bottom boundary layer, gravity currents in rotating systems, eddies, waves, circulation, and mixing.
Abstract: This book covers the following topics: recent developments in three dimensional and unsteady turbulence boundary-layer computations; flows far from equilibrium via molecular dynamics; physics of convention-solidification interaction; the continental shelf bottom boundary layer; gravity currents in rotating systems; strange attractors in fluids: another view; eddies, waves, circulation, and mixing: statistical geofluid mechanics; regular and mach reflection of shock waves; ship propellers; coherent structures; the critical layer and stability; general circulation of the oceans; characteristic-based schemes for the euler equations; vortex flows in aerodynamics; steady and unsteady boundary-layer separation; and wind wave prediction.
183 citations
TL;DR: The primary goal of this article is to summarize the FDA initiative and to report recent findings from the benchmark blood pump model study, which aided the development of an FDA Guidance Document on factors to consider when reporting computational studies in medical device regulatory submissions.
Abstract: Computational fluid dynamics (CFD) is increasingly being used to develop blood-contacting medical devices. However, the lack of standardized methods for validating CFD simulations and blood damage predictions limits its use in the safety evaluation of devices. Through a U.S. Food and Drug Administration (FDA) initiative, two benchmark models of typical device flow geometries (nozzle and centrifugal blood pump) were tested in multiple laboratories to provide experimental velocities, pressures, and hemolysis data to support CFD validation. In addition, computational simulations were performed by more than 20 independent groups to assess current CFD techniques. The primary goal of this article is to summarize the FDA initiative and to report recent findings from the benchmark blood pump model study. Discrepancies between CFD predicted velocities and those measured using particle image velocimetry most often occurred in regions of flow separation (e.g., downstream of the nozzle throat, and in the pump exit diffuser). For the six pump test conditions, 57% of the CFD predictions of pressure head were within one standard deviation of the mean measured values. Notably, only 37% of all CFD submissions contained hemolysis predictions. This project aided in the development of an FDA Guidance Document on factors to consider when reporting computational studies in medical device regulatory submissions. There is an accompanying podcast available for this article. Please visit the journal's Web site (www.asaiojournal.com) to listen.
96 citations
TL;DR: Comparable PGs were found among the TAVs in different models; pinwheeling indices were found to be different between both T AVs; turbulence patterns among both Tavs translated according to RSS were different; and both TAV's exhibit peak maximal RSS that exceeds platelet activation 100 Pa threshold limit.
66 citations
TL;DR: This review summarizes approaches to continuum-level modeling of hemolysis, a method that is likely to be useful well into the future for design of typical cardiovascular devices and to validate numerical simulations.
Abstract: Despite decades of research related to hemolysis, the accuracy of prediction algorithms for complex flows leaves much to be desired. Fundamental questions remain about how different types of fluid stresses translate to red cell membrane failure. While cellular- and molecular-level simulations hold promise, spatial resolution to such small scales is computationally intensive. This review summarizes approaches to continuum-level modeling of hemolysis, a method that is likely to be useful well into the future for design of typical cardiovascular devices. Weaknesses are revealed for the Eulerian method of hemolysis prediction and for the linearized damage function. Wide variations in scaling of red cell membrane tension are demonstrated with different types of fluid stresses when the scalar fluid stress is the same, as well as when the energy dissipation rate is the same. New experimental data are needed for red cell damage in simple flows with controlled levels of different types of stresses, including laminar shear, laminar extension (normal), turbulent shear, and turbulent extension. Such data can be curve-fit to create more universal continuum-level models and can serve to validate numerical simulations.
61 citations
TL;DR: It is shown for the first time that SH-coated surfaces may be a promising direction to minimize thrombotic complications in complex devices such as heart valves.
Abstract: In this study, we explore how blood-material interactions and hemodynamics are impacted by rendering a clinical quality 25 mm St. Jude Medical Bileaflet mechanical heart valve (BMHV) superhydrophobic (SH) with the aim of reducing thrombo-embolic complications associated with BMHVs. Basic cell adhesion is evaluated to assess blood-material interactions, while hemodynamic performance is analyzed with and without the SH coating. Results show that a SH coating with a receding contact angle (CA) of 160° strikingly eliminates platelet and leukocyte adhesion to the surface. Alternatively, many platelets attach to and activate on pyrolytic carbon (receding CA = 47), the base material for BMHVs. We further show that the performance index increases by 2.5% for coated valve relative to an uncoated valve, with a maximum possible improved performance of 5%. Both valves exhibit instantaneous shear stress below 10 N/m2 and Reynolds Shear Stress below 100 N/m2. Therefore, a SH BMHV has the potential to relax the requirement for antiplatelet and anticoagulant drug regimens typically required for patients receiving MHVs by minimizing blood-material interactions, while having a minimal impact on hemodynamics. We show for the first time that SH-coated surfaces may be a promising direction to minimize thrombotic complications in complex devices such as heart valves.
43 citations
References
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TL;DR: The rapid diffusion of nitric oxide between cells allows it to locally integrate the responses of blood vessels to turbulence, modulate synaptic plasticity in neurons, and control the oscillatory behavior of neuronal networks.
Abstract: Nitric oxide contrasts with most intercellular messengers because it diffuses rapidly and isotropically through most tissues with little reaction but cannot be transported through the vasculature due to rapid destruction by oxyhemoglobin. The rapid diffusion of nitric oxide between cells allows it to locally integrate the responses of blood vessels to turbulence, modulate synaptic plasticity in neurons, and control the oscillatory behavior of neuronal networks. Nitric oxide is not necessarily short lived and is intrinsically no more reactive than oxygen. The reactivity of nitric oxide per se has been greatly overestimated in vitro because no drain is provided to remove nitric oxide. Nitric oxide persists in solution for several minutes in micromolar concentrations before it reacts with oxygen to form much stronger oxidants like nitrogen dioxide. Nitric oxide is removed within seconds in vivo by diffusion over 100 microns through tissues to enter red blood cells and react with oxyhemoglobin. The direct toxicity of nitric oxide is modest but is greatly enhanced by reacting with superoxide to form peroxynitrite (ONOO-). Nitric oxide is the only biological molecule produced in high enough concentrations to out-compete superoxide dismutase for superoxide. Peroxynitrite reacts relatively slowly with most biological molecules, making peroxynitrite a selective oxidant. Peroxynitrite modifies tyrosine in proteins to create nitrotyrosines, leaving a footprint detectable in vivo. Nitration of structural proteins, including neurofilaments and actin, can disrupt filament assembly with major pathological consequences. Antibodies to nitrotyrosine have revealed nitration in human atherosclerosis, myocardial ischemia, septic and distressed lung, inflammatory bowel disease, and amyotrophic lateral sclerosis.
5,370 citations
1,595 citations
TL;DR: In this article, the authors survey the existing work on intermittency, refined similarity hypotheses, anomalous scaling exponents, derivative statistics, and intermittency models, and the structure and kinematics of small-scale structure.
Abstract: Small-scale turbulence has been an area of especially active research in the recent past, and several useful research directions have been pursued. Here, we selectively review this work. The emphasis is on scaling phenomenology and kinematics of small-scale structure. After providing a brief introduction to the classical notions of universality due to Kolmogorov and others, we survey the existing work on intermittency, refined similarity hypotheses, anomalous scaling exponents, derivative statistics, intermittency models, and the structure and kinematics of small-scale structure—the latter aspect coming largely from the direct numerical simulation of homogeneous turbulence in a periodic box.
1,183 citations
"Theory to predict shear stress on c..." refers background in this paper
...Thus, the true depiction of micro-environment of cells in realistic turbulent flows corresponds to their tumultuous experiences in a spectrum of dissipative eddies ranging from subKolmogorov scales all the way to the Taylor micro-scale that demarks the largest of the dissipative eddies [6]....
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...Another aspect that is important to consider is the notion of universality of turbulent structures despite the intermittency issue [6]....
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...In fact, there exist eddies that are a fraction of the Kolmogorov eddy, so called sub-Kolmogorov eddies, arising from the inherently intermittent nature of the instantaneous energy dissipation rate field [5,6]....
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TL;DR: Objections have been made from a theoretical point of view that the results of investigations of the viscosity of the blood in comparatively wide capillary tubes probably do not apply to the conditions in the narrower parts of the vascular system, whereby these authors especially seem to have had the true capillaries in view.
Abstract: Nearly one hundred years have passed since the French physician Poiseuille (1) took up for consideration the important problem of the resistance of the bloodstream in the narrow parts of the vascular system. As experimental difficulties arose with blood, his fundamental investigations were contied to experiments with water and different fluids in glass capillaries w He found, as is well known, that the time of efflux of a given volume of fluid is directly as the length of the tube, inversely as the difference of pressure at the two ends and inversely as the fourth power of the diameter. During the following time the law of Poiseuille seems to have been generally accepted with regard to the blood also and the results of the first experimental studies by Ewald (2) and Benno Lewy (3) were, like those of many re-examinations, in accordance with the law in question. The now prevailing opinion is that the blood behaves as a real fluid in the vascular system with regard to its viscosity (see the survey by Neuschlosz, 4). Against this opinion, however, objections have been made from a theoretical point of view. Von Kries (5) and Hiirthle (6) have pointed out that the results of investigations of the viscosity of the blood in comparatively wide capillary tubes probably do not apply to the conditions in the narrower parts of the vascular system, whereby these authors especially seem to have had the true capillaries in view. As far as we know, the only statement in the literature regarding the viscosity of the blood being altered in narrow capillary tubes is found in the paper of Denning and Watson (7) In the narrowest capillary employed in their researches, namely, one of a diameter of 0.3 mm., they observed increased values. This result is, however, certainly erroneous, for reasons that will be given below. It is true that the viscosity of the blood has been earlier investigated in capillary tubes, where a divergence from the law of Poiseuille-corresponding to our own results-ought to appear. Thus Hess (8) has examined the viscosity of the same blood in capillaries of a diameter of 0.239 and 0.126 mm. respectively under the same conditions. A calculation on the basis
1,154 citations