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Influence of the ventilation on the transport properties in the healthy and inflamed lung

Abstract : The main function of the lung is to supply the blood with oxygen and to drain the carbon dioxide from it. The lung captures the oxygen present in the ambient air where it rejects the carbon dioxide taken from the blood. This exchange results from the process of the lung's ventilation that repeatedly makes a volume of ambient air enter and leave the lung. In an idealized view, the ventilation can be characterized by two parameters: the maximum air velocity in the trachea (the amplitude) and the breathing frequency (the period). The goal of this thesis is to study and model the process of oxygen and carbon dioxide transport and exchanges in the lung. Gas transport is modeled by convection-diffusion-reaction equations in an idealized lung. A mathematical analysis of the model has been performed to prove the existence of a unique solution along with an asymptotic periodicity in time. Numerical simulations were performed to study a wide range of physiological configurations. In the healthy human case, the amounts of gas exchanged predicted by our model are close to physiology. The viscous and elastic energies spent during inspiration were then minimized assuming that our body needs in oxygen can be represented in our model by a constraint on the oxygen flow exchanged with the blood. Simulations were carried out for humans but also for any mammals using allometric scaling laws. The predictions of our model show that the ventilation parameters in mammals might be optimized to cost as little energy as possible. Then, we focused on the lung's ventilation of a human subject suffering from a pulmonary infection. The spread of a bronchial infection has been modeled in an idealized way and we studied how the ventilation is affected by the response of the immune system through bronchi wall inflammation. Our results show that the location of the transition zone between convection and diffusion mainly influence the quantity of oxygen exchanged with the blood. The location of this transition can be affected by the infection and hence alter the efficiency of the ventilation and modify its optimal configuration. Finally, to better understand the efficiency of a drug treatment delivered by aerosol, we modeled the deposit of aerosol particles in the first bifurcation of the bronchi of the human lung. Our model takes into account the evolution of the radius of the particles due to the exchange of water vapor and the evolution of the temperature of the particles due to the change of the surrounding environment. Our results show that the modeling of these parameters is important to represent more accurately the deposit of the particles on the walls of the bronchi. This work allows to better understand how the process of lung’s ventilation is adjusted and how it is affected by lung’s pathologies. Moreover, it highlights how ventilation can be used efficiently as a way to deliver drugs in the body.
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Submitted on : Tuesday, May 11, 2021 - 12:19:09 PM
Last modification on : Monday, October 11, 2021 - 5:08:09 PM


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  • HAL Id : tel-03156080, version 2



Frédérique Noël. Influence of the ventilation on the transport properties in the healthy and inflamed lung. Modeling and Simulation. Université Côte d'Azur, 2021. English. ⟨NNT : 2021COAZ4004⟩. ⟨tel-03156080v2⟩



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