Two dimensional computational model coupling myoarchitecture-based lingual tissue mechanics with liquid bolus flow during oropharyngeal swallowing.

Biomechanical relationships involving lingual myoanatomy, contractility, and bolus movement are fundamental properties of human swallowing. To portray the relationship between lingual deformation and bolus flow during swallowing, a weakly one-way solid-fluid finite element model (FEM) was derived employing an elemental mesh aligned to magnetic resonance diffusional tractography (Q-space MRI, QSI) of the human tongue, an arbitrary Lagrangian-Eulerian (ALE) formulation with remeshing to account for the effects of lingual surface (boundary) deformation, an implementation of patterned fiber shortening, and a computational visualization of liquid bolus flow. Representing lingual tissue deformation in terms of its 2D principal Lagrangian strain in the mid-sagittal plane, we demonstrated that the swallow sequence was characterized by initial superior-anterior expansion directed towards the hard palate, followed by sequential, radially directed, contractions of the genioglossus and verticalis to promote lingual rotation (lateral perspective) and propulsive displacement.

Percutaneous mitral valve dilatation: single balloon versus double balloon. A finite element study.

Background And Aim Of The Study: Percutaneous mitral valve (MV) dilatation is routinely performed for mitral stenosis using either a single balloon (SB) or double balloon (DB) technique. The study aim was to compare the two techniques using the finite element (FE) method.

Methods: An established FE model of the MV was modified by fusing MV leaflet edges at commissure level to simulate a stenotic valve (orifice area = 180 mm2).

The usefulness of the line spread test as a measure of liquid consistency.

Although dietary modification is a common treatment strategy used to manage dysphagic patients who aspirate thin liquids, there are no standard definitions for thickened liquid preparation. This lack of standardization leads to variability in practice and points to the need for a simple tool for clinicians to assess thickened liquid consistency. The current study analyzed the utility of the Line Spread Test (LST) in this regard.

Function of longitudinal vs circular muscle fibers in esophageal peristalsis, deduced with mathematical modeling.

We summarize from previous works the functions of circular vs. longitudinal muscle in esophageal peristaltic bolus transport using a mix of experimental data, the conservation laws of mechanics and mathematical modeling. Whereas circular muscle tone generates radial closure pressure to create a local peristaltic closure wave, longitudinal muscle tone has two functions, one physiological with mechanical implications, and one purely mechanical.

A planar finite element model of bolus containment in the oral cavity.

As individuals age, one of the objective changes that occurs in the oropharyngeal swallow is the development of a delay between bolus entry into the pharynx and the initiation of airway protection mechanisms. For longer delays, this phenomenon is sometimes referred to as "premature spillage," and it has been suggested that such spillage, which is a risk factor for dysphagia, may be associated with pre-swallow lingual gestures, or "tongue pumping." The goal of the current study was to develop a simplified two-dimensional computational model of the oropharynx to simulate the containment of a Newtonian fluid bolus within the oral cavity in response to a given pattern of lingual gestures for different viscosities.

A theoretical framework to analyze bend testing of soft tissue.

It has been hypothesized that repetitive flexural stresses contribute to the fatigue-induced failure of bioprosthetic heart valves. Although experimental apparatuses capable of measuring the bending properties of biomaterials have been described, a theoretical framework to analyze the resulting data is lacking. Given the large displacements present in these bending experiments and the nonlinear constitutive behavior of most biomaterials, such a formulation must be based on finite elasticity theory.

The effects of intraoral pressure sensors on normal young and old swallowing patterns.

Lingual pressure generation plays a crucial role in oropharyngeal swallowing. To more discretely study the dynamic oropharyngeal system, a 3-bulb array of pressure sensors was designed with the Kay Elemetrics Corporation (Lincoln Park, NJ). The influence of the device upon normal swallowing mechanics and boluses representative of flow relative to age and bolus condition was the focus of this study.

Non-linear fluid-coupled computational model of the mitral valve.

Background And Aim Of The Study: The dynamics of the mitral valve result from the synergy of left heart geometry, local blood flow and tissue integrity. Herein is presented the first coupled fluid-structure computational model of the mitral valve in which valvular kinematics result from the interaction of local blood flow and a continuum representation of valvular microstructure.

Methods: The diastolic geometry of the mitral valve was assembled from previously published experimental data.

The relationship of normal and abnormal microstructural proliferation to the mitral valve closure sound.

Background: Many diseases that affect the mitral valve are accompanied by the proliferation or degradation of tissue microstructure. The early acoustic detection of these changes may lead to the better management of mitral valve disease. In this study, we examine the nonstationary acoustic effects of perturbing material parameters that characterize mitral valve tissue in terms of its microstructural components.

Mechanics and hemodynamics of esophageal varices during peristaltic contraction.

Our hypothesis states that variceal pressure and wall tension increase dramatically during esophageal peristaltic contractions. This increase in pressure and wall tension is a natural consequence of the anatomy and physiology of the esophagus and of the esophageal venous plexus. The purpose of this study was to evaluate variceal hemodynamics during peristaltic contraction.

A coupled fluid-structure finite element model of the aortic valve and root.

Background And Aim Of The Study: The study aim was to develop a three-dimensional coupled fluid-structure finite element model of the aortic valve and root. This model extends previous purely structural finite element models, and represents a significant step toward realistic simulation of the complex interactions among tissue material properties and valvular function.

Methods: The aortic root and valve geometry were extracted from magnetic resonance images and imported into the LS-Dyna explicit finite element package.

A mathematical model for estimating muscle tension in vivo during esophageal bolus transport.

We present a model of esophageal wall muscle mechanics during bolus transport with which the active and "passive" components of circular muscle tension are separately extracted from concurrent manometric and videofluoroscopic data. Local differential equations of motion are integrated across the esophageal wall to yield global equations of equilibrium which relate total tension within the esophageal wall to intraluminal pressure and wall geometry. To quantify the "passive" (i.

Biaxial mechanical properties of porcine ascending aortic wall tissue.

Background And Aim Of The Study: Biaxial mechanical properties have been reported for porcine aortic valve leaflets, but not for the aortic root wall. These data are important for understanding the relationship between tissue material properties and function, providing a baseline for diseased tissue, and for providing a basis for numerical models of aortic mechanics. The study aim was to determine the biaxial material properties of porcine aortic root wall tissue.