In silico parametric analysis of femoro-jugular venovenous ECMO and return cannula dynamics: In silico analysis of femoro-jugular VV ECMO.

Background: Increasingly, computational fluid dynamics (CFD) is helping explore the impact of variables like: cannula design/size/position/flow rate and patient physiology on venovenous (VV) extracorporeal membrane oxygenation (ECMO). Here we use a CFD model to determine what role cardiac output (CO) plays and to analyse return cannula dynamics.

Methods: Using a patient-averaged model of the right atrium and venae cava, we virtually inserted a 19Fr return cannula and a 25Fr drainage cannula.

Estimation of the concentration boundary layer adjacent to a flat surface using computational fluid dynamics.

Dissolution-permeation (D/P) experiments are widely used during preclinical development due to producing results with better predictability than traditional monophasic experiments. However, it is difficult to compare absorption across in vitro setups given the propensity to only report apparent permeability. We therefore developed an approach to predict the concentration boundary layer for any D/P device by using computational fluid dynamics (CFD).

Assessment of Rheological Models Applied to Blood Flow in Human Thoracic Aorta.

Purpose: The purpose of this study is to assess the importance of non-Newtonian rheological models on blood flow in the human thoracic aorta.

Methods: The pulsatile flow in the aorta is simulated using the models of Casson, Quemada and Walburn-Schneck in addition to a case of fixed (Newtonian) viscosity. The impact of the four rheological models (using constant hematocrit) was assessed with respect to (i) magnitude and deviation of the viscosity relative to a reference value (the Newtonian case); (ii) wall shear stress (WSS) and its time derivative; (iii) common WSS-related indicators, OSI, TAWSS and RRT; (iv) relative volume and surface-based retrograde flow; and (v) the impact of rheological models on the transport of small particles in the thoracic aorta.

Effect of flow rate ratio and positioning on a lighthouse tip ECMO return cannula.

Extracorporeal membrane oxygenation is a life-saving support therapy in the case of cardiopulmonary refractory failure. Its use is associated to complications due to the presence of artificial surfaces and supraphysiological stress conditions. Thus, knowledge of the fluid structures associated to each component can give insight into sources of blood damage.

Hemodynamic and recirculation performance of dual lumen cannulas for venovenous extracorporeal membrane oxygenation.

Venovenous extracorporeal membrane oxygenation (ECMO) can be performed with two single lumen cannulas (SLCs) or one dual-lumen cannula (DLC) where low recirculation fraction ([Formula: see text]) is a key performance criterion. DLCs are widely believed to have lower [Formula: see text], though these have not been directly compared. Similarly, correct positioning is considered critical although its impact is unclear.

Numerical and experimental investigation of a lighthouse tip drainage cannula used in extracorporeal membrane oxygenation.

Background: Extracorporeal membrane oxygenation is a life-saving therapy used in case of acute respiratory/circulatory failure. Exposure of blood to non-physiological surfaces and high shear stresses is related to hemolytic damage and platelet activation. A detailed knowledge of the fluid dynamics of the components under different scenarios is thus paramount to assess the thrombogenicity of the circuit.

Cannulation configuration and recirculation in venovenous extracorporeal membrane oxygenation.

Venovenous extracorporeal membrane oxygenation is a treatment for acute respiratory distress syndrome. Femoro-atrial cannulation means blood is drained from the inferior vena cava and returned to the superior vena cava; the opposite is termed atrio-femoral. Clinical data comparing these two methods is scarce and conflicting.

Red blood cell distribution width is associated with increased interactions of blood cells with vascular wall.

The mechanism underlying the association between elevated red cell distribution width (RDW) and poor prognosis in variety of diseases is unknown although many researchers consider RDW a marker of inflammation. We hypothesized that RDW directly affects intravascular hemodynamics, interactions between circulating cells and vessel wall, inducing local changes predisposing to atherothrombosis. We applied different human and animal models to verify our hypothesis.

Impact of altered vena cava flow rates on right atrium flow characteristics.

The right atrium (RA) combines the superior vena cava (SVC) and inferior vena cava (IVC) flows. Treatments like extracorporeal membrane oxygenation (ECMO) and hemodialysis by catheter alter IVC/SVC flows. Here we assess how altered IVC/SVC flow contributions impact RA flow.

Roughness-dependent clogging of particle suspensions flowing into a constriction.

When concentrated particle suspensions flow into a constricting channel, the suspended particles may either smoothly flow through the constriction or jam and clog the channel. These clogging events are typically detrimental to technological processes, such as in the printing of dense pastes or in filtration, but can also be exploited in micro-separation applications. Many studies have to date focused on important parameters influencing the occurrence of clogs, such as flow velocity, particle concentration, and channel geometry.

Blood Pumps for Extracorporeal Membrane Oxygenation: Platelet Activation During Different Operating Conditions.

Extracorporeal membrane oxygenation (ECMO) is a therapy used in severe cardiopulmonary failure. Blood is pumped through an artificial circuit exposing it to nonphysiologic conditions, which promote platelet activation and coagulation. Centrifugal pumps used at lower flow rates than their design point may lose pump efficiency and increase the risk of hemolysis.

Flow Dynamics and Mixing in Extracorporeal Support: A Study of the Return Cannula.

Cannulation strategies in medical treatment such as in extracorporeal life support along with the associated cannula position, orientation and design, affects the mixing and the mechanical shear stress appearing in the flow field. This in turn influences platelet activation state and blood cell destruction. In this study, a co-flowing confined jet similar to a return cannula flow configuration found in extracorporeal membrane oxygenation was investigated experimentally.

Flows and function of the Infant Flow neonatal continuous positive airway pressure device investigated with computational fluid dynamics.

Aim: The first dedicated neonatal continuous positive airway pressure (CPAP) device using variable flow was the Infant Flow. The system was pressure stable with a low resistance to breathing. The aim of this study was to describe the flow and function of the Infant Flow geometry using simulated breathing and computational fluid dynamics.

Pressure and flow properties of dual-lumen cannulae for extracorporeal membrane oxygenation.

Introduction: In the last decade, dual-lumen cannulae have been increasingly applied in patients undergoing extracorporeal life support. Well-performing vascular access is crucial for efficient extracorporeal membrane oxygenation support; thus, guidance for proper cannulae size is required. Pressure-flow charts provided by manufacturers are often based on tests performed using water, rarely blood.

An experimental model of veno-venous arterial extracorporeal membrane oxygenation.

Introduction: Veno-venous arterial extracorporeal membrane oxygenation is a hybrid-modality of extracorporeal membrane oxygenation combining veno-venous and veno-arterial extracorporeal membrane oxygenation. It may be applied to patients with both respiratory and cardio-circulatory failure.

Aim: To describe a computational spreadsheet regarding an ex vivo experimental model of veno-venous arterial extracorporeal membrane oxygenation to determine the return of cannula pairs in a single pump-driven circuit.

Modeling sensitivity and uncertainties in platelet activation models applied on centrifugal pumps for extracorporeal life support.

Two platelet activation models were studied with respect to uncertainties of model parameters and variables. The sensitivity was assessed using two direct/deterministic approaches as well as the statistical Monte Carlo method. The first two, are linear in character whereas the latter is non-linear.

Pressure and flow properties of cannulae for extracorporeal membrane oxygenation I: return (arterial) cannulae.

Adequate extracorporeal membrane oxygenation support in the adult requires cannulae permitting blood flows up to 6-8 L/minute. In accordance with Poiseuille's law, flow is proportional to the fourth power of cannula inner diameter and inversely proportional to its length. Poiseuille's law can be applied to obtain the pressure drop of an incompressible, Newtonian fluid (such as water) flowing in a cylindrical tube.

Pressure and flow properties of cannulae for extracorporeal membrane oxygenation II: drainage (venous) cannulae.

The use of extracorporeal life support devices such as extracorporeal membrane oxygenation in adults requires cannulation of the patient's vessels with comparatively large diameter cannulae to allow circulation of large volumes of blood (>5 L/min). The cannula diameter and length are the major determinants for extracorporeal membrane oxygenation flow. Manufacturing companies present pressure-flow charts for the cannulae; however, these tests are performed with water.

Flow-induced platelet activation in components of the extracorporeal membrane oxygenation circuit.

Extracorporeal membrane oxygenation (ECMO) is used for rescue in severe respiratory and/or circulatory failure. The patient's blood is pumped over artificial surfaces in the ECMO circuit. A platelet activation model was applied to study the potential thrombogenicity of ECMO circuit components: the centrifugal blood pump, cannulae, and tubing connectors.

Detection of Thrombosis in the Extracorporeal Membrane Oxygenation Circuit by Infrasound: Proof of Concept.

As of today, there exist no reliable, objective methods for early detection of thrombi in the extracorporeal membrane oxygenators (ECMO) system. Within the ECMO system, thrombi are not always fixed to a certain component or location in the circuit. Thus, clot fragments of different shapes and consistencies may circulate and give rise to vibrations and sound generation.

Nanofibril Alignment in Flow Focusing: Measurements and Calculations.

Alignment of anisotropic supermolecular building blocks is crucial to control the properties of many novel materials. In this study, the alignment process of cellulose nanofibrils (CNFs) in a flow-focusing channel has been investigated using small-angle X-ray scattering (SAXS) and modeled using the Smoluchowski equation, which requires a known flow field as input. This flow field was investigated experimentally using microparticle-tracking velocimetry and by numerically applying the two-fluid level set method.

Effects of aortic irregularities on blood flow.

Anatomic aortic anomalies are seen in many medical conditions and are known to cause disturbances in blood flow. Turner syndrome (TS) is a genetic disorder occurring only in females where cardiovascular anomalies, particularly of the aorta, are frequently encountered. In this study, numerical simulations are applied to investigate the flow characteristics in four TS patient- related aortic arches (a normal geometry, dilatation, coarctation and elongation of the transverse aorta).

Hydrodynamic alignment and assembly of nanofibrils resulting in strong cellulose filaments.

Cellulose nanofibrils can be obtained from trees and have considerable potential as a building block for biobased materials. In order to achieve good properties of these materials, the nanostructure must be controlled. Here we present a process combining hydrodynamic alignment with a dispersion-gel transition that produces homogeneous and smooth filaments from a low-concentration dispersion of cellulose nanofibrils in water.

Atherosclerotic indicators for blood-like fluids in 90-degree arterial-like bifurcations.

The identification of regions prone to atherogenesis in the arterial network is compounded by the complex, slow interaction of mechanical and biomechanical processes. In recent times simplifications to the analysis of the near wall hemodynamics have been sought-after to identify plaque prone regions. Mean parameters have been defined to analyze the common fluid mechanical hypotheses considering the role of wall shear stress (WSS) variations in the pathological changes to the endothelium.

Wall shear stress variations and unsteadiness of pulsatile blood-like flows in 90-degree bifurcations.

Complex and slow interaction of different mechanical and biochemical processes in hemodynamics is believed to govern atherogenesis. Over the last decades studies have shown that fluid mechanical factors such as the Wall Shear Stress (WSS) and WSS gradients can play an important role in the pathological changes of the endothelium. This study provides further indications that the effects of fluid mechanical aspects are correlated with the diseased regions of the larger arteries.