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Resumen La dinamica de fluidos computacional (CFD) se define como la tecnica informatica que busca la simulacion del movimiento de los fluidos. Las principales ventajas de la tecnica de CFD sobre otro tipo de estudios de mecanica de fluidos son la reduccion sustancial de tiempo y costes en los experimentos, la posibilidad de analizar sistemas o condiciones muy dificiles de simular experimentalmente, como es el caso de las vias aereas, y un nivel de detalle practicamente ilimitado. Utilizamos el programa de CFD Ansys-Fluent para elaborar un modelo de la via aerea de conduccion que permite la simulacion de distintos caudales de flujo inspiratorio, asi como del deposito de particulas inhaladas de diferentes diametros, obteniendo resultados concordantes con la literatura existente utilizando otros procedimientos. De este modo se pretende abrir una nueva via a la individualizacion de los tratamientos para las distintas patologias respiratorias.

Computational Fluid Dynamics (CFD) is a computer-based tool for simulating fluid movement. The main advantages of CFD over other fluid mechanics studies include: substantial savings in time and cost, the analysis of systems or conditions that are very difficult to simulate experimentally (as is the case of the airways), and a practically unlimited level of detail. We used the Ansys-Fluent CFD program to develop a conducting airway model to simulate different inspiratory flow rates and the deposition of inhaled particles of varying diameters, obtaining results consistent with those reported in the literature using other procedures. We hope this approach will enable clinicians to further individualize the treatment of different respiratory diseases.

Resumen La medicacion inhalada constituye el tratamiento de primera linea de enfermedades como el asma o la enfermedad pulmonar obstructiva cronica. Su efectividad esta en relacion con la cantidad de farmaco que logre depositarse mas alla de la region orofaringea, con el lugar en que se produzca el deposito y con la distribucion uniforme o no del mismo. Otros factores trascendentes son el tamano de las particulas inhaladas, las condiciones de respiracion, la geometria de las vias aereas y los mecanismos de aclaramiento mucociliar. Actualmente se estan aplicando modelos matematicos que permiten describir el deposito de farmacos inhalados a partir del tamano de las moleculas, el flujo inspiratorio y la distribucion anatomica del arbol bronquial. El deposito de particulas en las vias aereas pequenas recibe la maxima atencion de las empresas farmaceuticas y es del maximo interes para poder controlar mejor a los pacientes que reciben estos farmacos.

Inhaled medication is the first-line treatment of diseases such as asthma or chronic obstructive pulmonary disease. Its effectiveness is related to the amount of drug deposited beyond the oropharyngeal region, the place where the deposit occurs and its distribution (uniform or not). It is also important to consider the size of the inhaled particles, the breathing conditions, the geometry of the airways and the mucociliary clearance mechanisms. Currently, mathematical models are being applied to describe the deposition of inhaled drugs based on the size of the particles, the inspiratory flow and the anatomical distribution of the bronchial tree. The deposition of particles in the small airways gets maximum attention from pharmaceutical companies and is of great interest as it is related with a better control in patients receiving these drugs.

Background: To validate the Test of Adherence to Inhalers' (TAI), a 12-item questionnaire designed to assess the adherence to inhalers in patients with COPD or asthma. Methods: A total of 1009 patients with asthma or COPD participated in a cross-sectional multicenter study. Patients with electronic adherence 80% were defined as adherents. Construct validity, internal validity, and criterion validity were evaluated. Self-reported adherence was compared with the Morisky-Green questionnaire. Results: Factor analysis study demonstrated two factors, factor 1 was coincident with TAI patient domain (items 1 to 10) and factor 2 with TAI health-care professional domain (items 11 and 12). The Cronbach's alpha was 0.860 and the test-retest reliability 0.883. TAI scores correlated with electronic adherence (=0.293, p=0.01). According to the best cut-off for 10 items (score 50, area under the ROC curve 0.7), 569 (62.5%) patients were classified as non-adherents. The non-adherence behavior pattern was: erratic 527 (57.9%), deliberate 375 (41.2%), and unwitting 242 (26.6%) patients. As compared to Morisky-Green test, TAI showed better psychometric properties. Conclusions: The TAI is a reliable and homogeneous questionnaire to identify easily non-adherence and to classify from a clinical perspective the barriers related to the use of inhalers in asthma and COPD., This study was funded by the Integrated Research Asthma Program (PII Asthma) together with the Integrated Research COPD Program (PII COPD) of the Spanish Respiratory Society (SEPAR). Unconditional funding was provided by Chiesi, who did not participate in data collection, interpretation of the results, or writing of the manuscript.

A three-dimensional, computational fluid dynamics model of the human respiratory system is put forward for consideration. This in silico model is based on existing state-of-the-art geometric approximations. As a complete simulation of the geometry would have unaffordable high computational costs, the model is composed of a single path of air from the mouth to the 16th bronchial generation, truncating the symmetrical branches that were not included. The innovation housed in this model is the development of a function that is applied to the truncated branches, which contemplates the behavior of the airflow within those branches, by copying cell by cell the velocity vectors existing in the symmetrical face of the developed branch. This model can reproduce the complete airflow process: inspiration and expiration cycles, through simulation in unsteady flow conditions. In normal breathing the air velocity varies within a narrow range, with steady changes. Therefore the model has been validated simulating a spir...

SummaryBackground The need for a better understanding of pulmonary diseases has led to increased interest in the development of realistic computational models of the human lung. Methods To minimize computational cost, a reduced geometry model is employed for a model lung airway geometry up to generation 16. Truncated airway branches require physiologically realistic boundary conditions to accurately represent the effect of the removed airway sections. A user-defined function has been developed which applies velocities mapped from similar locations in fully resolved airway sections. The methodology can be applied in any general purpose computational fluid dynamics code, with the only limitation that the lung model must be symmetrical in each truncated branch. Results Unsteady simulations have been performed to verify the operation of the model. The test case simulates a spirometry since the lung is obliged to rapidly perform both inspiration and expiration. Once the simulation was completed, the obtained pressure in the lower level of the lung was used as a boundary condition. The output velocity, which is a numerical spirometry, was compared with the experimental spirometry for validation purposes. Conclusions This model can be applied for a wide range of patient-specific resolution levels. If the upper airway generations have been constructed from a computed tomography (CT) scan, it would be possible to quickly obtain a complete reconstruction of the lung specific to a specific person, which would allow individualized therapies. This article is protected by copyright. All rights reserved.

This paper presents a general methodology for the development and simulation of a human lung between scales 0–16. The methodology is based on the simulation of only one of the two possible branches at each bronchiole. The operation of the truncated branches is included by means of a user-defined function. This function prescribes the velocity profile calculated for the active branches in the truncated ones in order to make the hydraulic losses equal between them. This procedure was tested between 0 and 7th generation by imposing the time profile of a real forced spirometry test in the trachea as boundary condition. The test showed a very good agreement between the numerical predictions and the spirometry data.Copyright © 2012 by ASME