Assessment of valve implantation in the descending aorta as an alternative for aortic regurgitation patients not treatable with conventional procedures.

BACKGROUND: Aortic Regurgitation (AR) produces the entrance of an abnormal amount of blood in the left ventricle. This disease is responsible for high morbidity and mortality worldwide and may be caused by an aortic valve dysfunction. Surgical and transcatheter aortic valve replacement (TAVR) are the current options for treating AR. They have replaced older procedures such as Hufnagel's one. However, some physicians have reconsidered this procedure as a less aggressive alternative for patients not eligible for surgical or TAVR. Although Hufnagel suggested a 75% regurgitation reduction when a valve is placed in the descending aorta, a quantification of this value has not been reported. METHODS: In this paper, CFD/FSI numerical simulation is conducted on an idealized geometry. We quantify the effect of placing a bileaflet mechanical heart valve in the descending aorta on a moderate-severe AR case. A three-element Windkessel model is employed to prescribe pressure outlet boundary conditions. We calculate the resulting flow rates and pressures at the aorta and first-generation vessels. Moreover, we evaluate several indices to assess the improvement due to the valve introduction. RESULTS AND CONCLUSIONS: Regurgitation fraction (RF) is reduced from 37.5% (without valve) to 18.0% (with valve) in a single cardiac cycle. This reduction clearly shows the remarkable efficacy of the rescued technique. It will further ameliorate the left ventricle function in the long-term. Moreover, the calculations show that the implantation in that location introduces fewer incompatibilities' risks than a conventional one. The proposed methodology can be extended to any particular conditions (pressure waveforms/geometry) and is designed to assess usual clinical parameters employed by physicians.

Construction of a hybrid lung model by combining a real geometry of the upper airways and an idealized geometry of the lower airways.

BACKGROUND AND OBJECTIVE: Health care costs represent a substantial an increasing percentage of global expenditures. One key component is treatment of respiratory diseases, which account for one in twelve deaths in Europe. Computational simulations of lung airflow have potential to provide considerable cost reduction and improved outcomes. Such simulations require accurate in silico modeling of the lung airway. The geometry of the lung is extremely complex and for this reason very simple morphologies have primarily been used to date. The objective of this work is to develop an effective methodology for the creation of hybrid pulmonary geometries combining patient-specific models obtained from CT images and idealized pulmonary models, for the purpose of carrying out experimental and numerical studies on aerosol/particle transport and deposition in inhaled drug delivery. METHODS: For the construction of the hybrid numerical model, lung images obtained from computed tomography were exported to the DICOM format to be treated with a commercial software to build the patient-specific part of the model. At the distal terminus of each airway of this portion of the model, an idealization of a single airway path is connected, extending to the sixteenth generation. Because these two parts have different endings, it is necessary to create an intermediate solid to link them together. Physically realistic treatment of truncated airway boundaries in the model was accomplished by mapping of the flow velocity distribution from corresponding conducting airway segments. RESULTS: The model was verified using two sets of simulations, steady inspiration/expiration and transient simulation of forced spirometry. The results showed that the hybrid model is capable of providing a realistic description of air flow dynamics in the lung while substantially reducing computational costs relative to models of the full airway tree. CONCLUSIONS: The model development outlined here represents an important step toward computational simulation of lung dynamics for patient-specific applications. Further research work may consist of investigating specific diseases, such as chronic bronchitis and pulmonary emphysema, as well as the study of the deposition of pollutants or drugs in the airways.

A method for measuring the interfacial tension for density-matched liquids.

We propose a method to measure the interfacial tension characterizing the interface between two immiscible liquids of practically the same density. In this method, a cylindrical liquid bridge made of one the liquids is vibrated laterally inside a tank filled with the other. The first resonance frequency is determined and equated to the first eigenfrequency of the m=1 linear mode to infer the interfacial tension value. The method does not involve the density jump across the interface. Therefore, its accuracy is affected neither by the smallness of the Bond number nor by errors of the density difference. The experimental setup is relatively simple, and the procedure does not use image processing techniques. The results satisfactorily agree with those measured by TIFA-AI (Theoretical Fitting Image Analysis-Axisymmetric Interfaces) for the same liquid bridges when the density difference is sufficiently large for TIFA-AI to be valid. We conduct numerical simulations of the Navier-Stokes equations to determine the best parameter conditions for the proposed method. The transfer function characterizing the frequency response of the fluid configuration is measured in some experiments to quantify non-linear effects and to study the role played by the outer bath vibration.

Simulation of the human airways using virtual topology tools and meshing optimization.

A method is proposed to improve the quality of the three-dimensional airway geometric models using a commercial software, checking the number of elements, meshing time, and aspect ratio and skewness parameters. The use of real and virtual topologies combined with patch-conforming and patch-independent meshing algorithms results in four different models being the best solution the combination of virtual topology and patch-independent algorithm, due to an excellent aspect ratio and skewness of the elements, and minimum meshing time. The result is a reduction in the computational time required for both meshing and simulation due to a smaller number of cells. The use of virtual topologies combined with patch-independent meshing algorithms could be extended in bioengineering because the geometries handling is similar to this case. The method is applied to a healthy person using their computed tomography images. The resulting numerical models are able to simulate correctly a forced spirometry.

Asthma education taught by physical education teachers at grade schools: A randomised cluster trial

Objective: Assess whether the Asthma, Sport and Health (ASAH) programme taught by teachers improves asthmatics’ quality of life, asthma knowledge, and reduces school absenteeism. Design: Randomised cluster trial parallel group. Participants: 2293 students (203 asthmatic) in the Intervention School group (IS) and 2214 in the Comparison School (CS) (224 asthmatic) belonging to primary school. Intervention: Implementation of the educational programme ‘Asthma, Sport and Health’ at grade schools, taught by physical education teachers. Main outcome: Quality of life according to the Pediatric Asthma Quality of Life Questionnaire (PAQLQ). Secondary outcomes: Asthma knowledge, asthma control, school absenteeism. Results: After implementing the programme in the IS group, global quality of life improved significantly (p < 0.001) as did their domains, symptoms (p < 0.001), emotional function (p < 0.001) and activity limitations ( p < 0.01), while in the CS group improvement was seen in global life quality (p < 0.01) without any significant changes in the domains for emotional function and activity limitations. Asthma knowledge only increased in IS, among asthmatic students from 16.51 (CI 95% 16.04-16.98) to 18.16 (CI 95% 17.69-18.62) (p < 0.001) and students without asthma from 15.49 (CI95% 15.36-15.63) to 17.50 (CI95% 17.36-17.64) (p < 0.001). The multiple regression analysis showed that quality of life and its domains depend on asthma knowledge and above all, having well-controlled asthma. We found no decrease in school absenteeism. Conclusions: The ASAH programme improved certain quality of life aspects regarding asthma (emotional function and limitation of activities) and asthma knowledge, but it failed to reduce school absenteeism NCT01607749 (AU)

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Asthma education taught by physical education teachers at grade schools: A randomised cluster trial.

OBJECTIVE: Assess whether the Asthma, Sport and Health (ASAH) programme taught by teachers improves asthmatics' quality of life, asthma knowledge, and reduces school absenteeism. DESIGN: Randomised cluster trial parallel group. PARTICIPANTS: 2293 students (203 asthmatic) in the Intervention School group (IS) and 2214 in the Comparison School (CS) (224 asthmatic) belonging to primary school. INTERVENTION: Implementation of the educational programme "Asthma, Sport and Health" at grade schools, taught by physical education teachers. MAIN OUTCOME: Quality of life according to the Pediatric Asthma Quality of Life Questionnaire (PAQLQ). SECONDARY OUTCOMES: Asthma knowledge, asthma control, school absenteeism. RESULTS: After implementing the programme in the IS group, global quality of life improved significantly (p<0.001) as did their domains, symptoms (p<0.001), emotional function (p<0.001) and activity limitations (p<0.01), while in the CS group improvement was seen in global life quality (p<0.01) without any significant changes in the domains for emotional function and activity limitations. Asthma knowledge only increased in IS, among asthmatic students from 16.51 (CI 95% 16.04-16.98) to 18.16 (CI 95% 17.69-18.62) (p<0.001) and students without asthma from 15.49 (CI95% 15.36-15.63) to 17.50 (CI95% 17.36-17.64) (p<0.001). The multiple regression analysis showed that quality of life and its domains depend on asthma knowledge and above all, having well-controlled asthma. We found no decrease in school absenteeism. CONCLUSIONS: The ASAH programme improved certain quality of life aspects regarding asthma (emotional function and limitation of activities) and asthma knowledge, but it failed to reduce school absenteeism NCT01607749.

Numerical and experimental analysis of the transitional flow across a real stenosis.

In this paper, we present a numerical study of the pulsatile transitional flow crossing a severe real stenosis located right in front of the bifurcation between the right subclavian and right common carotid arteries. The simulation allows one to determine relevant features of this subject-specific flow, such as the pressure waves in the right subclavian and right common carotid arteries. We explain the subclavian steal syndrome suffered by the patient in terms of the drastic pressure drop in the right subclavian artery. This pressure drop is caused by both the diverging part of the analyzed stenosis and the reverse flow in the bifurcation induced by another stenosis in the right internal carotid artery.

Dynamics of an axisymmetric liquid bridge close to the minimum-volume stability limit.

We analyze both theoretically and experimentally the dynamical behavior of an isothermal axisymmetric liquid bridge close to the minimum-volume stability limit. First, the nature of this stability limit is investigated experimentally by determining the liquid bridge response to a mass force pulse for volumes just above that limit. In our experiments, the liquid bridge breakup takes place only when the critical volume is surpassed and is never triggered by the mass force pulse. Second, the growth of the small-amplitude perturbation mode initiating the liquid bridge breakage is measured experimentally and calculated from the linearized Navier-Stokes equations. The results of the linear stability analysis allow one to explain why liquid bridges with volumes just above the stability limit are so robust. Finally, the nonlinear process leading to the liquid bridge breakup is described from both experimental data and the solution of the full Navier-Stokes equations. Special attention is paid to the free-surface pinchoff. The results show that the flow becomes universal (independent of both the initial and boundary conditions) sufficiently close to that singularity and suggest that the transition from the inviscid to the viscous regime is about to take place in the final stage of both the experiments and numerical simulations.

Sub-micrometer precision of optical imaging to locate the free surface of a micrometer fluid shape.

In this note, we explore the precision of the optical imaging method for measuring the free surface position of a micrometer fluid shape. For this purpose, images of a liquid film deposited on a rod were acquired and processed. The resulting contour was compared with the corresponding solution to the Young-Laplace equation. The average deviation was about 30nm, 25 times smaller than the pixel size, reflecting the validity of optical imaging for most applications in microfluidics.

Office-based testing for antibody to human immunodeficiency virus in urology patients.

Knowledge of the status of a patient regarding antibody to human immunodeficiency virus type 1 (HIV-1) may be important in many clinical situations. Consequently, we evaluated a rapid test for antibody to HIV-1 peptides that might be suitable for a physician office practice. We evaluated the time necessary to learn to do the test, and test performance using a reference panel and a seroconversion panel as well as 200 clinical specimens. Personnel who were previously unfamiliar with immunoassays learned the test procedure within 30 minutes. All reference specimens were interpreted correctly. One clinical sample reacted in the test but the result was not confirmed by Western blot. The rapid, peptide-based test was easy to use and performance was comparable to currently licensed tests performed at clinical laboratories.

Evaluation of blood collected on filter paper for detection of antibodies to human immunodeficiency virus type 1.

This study was undertaken to evaluate the sensitivity and specificity of a commercial enzyme immunoassay in detecting antibody to human immunodeficiency virus type 1 using whole-blood specimens collected onto filter paper. Results obtained with specimens collected onto filter paper were comparable with those obtained with the corresponding serum or plasma specimens.