Interplay Between Optimal Ventilation and Gas Transport in a Model of the Human Lung

Noël, Frédérique; Mauroy, Benjamin

doi:10.3389/fphys.2019.00488

Cited by 15 publications

(55 citation statements)

References 41 publications

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“…However, the model must be able to qualitatively reproduce such data and, above all, to highlight interesting phenomena, in particular to shed new light on clinical data/experimental observations. In this sense, the model we are building here and the use we make of it is quite in line with many previous works (Van Muylem et al, 2003;Kerckx et al, 2008;Warren et al, 2010;Florens et al, 2011a;Karamaoun et al, 2018a,b;Wells et al, 2018;Noel and Mauroy, 2019;Park et al, 2019).…”

Section: Introductionsupporting

confidence: 84%

“…The generation index within an acinus is written m ( m = 1, …, 7). As in the work of Noel and Mauroy ( 2019 ), we assume that all the airways within an acinus are right circular cylinders of length L a and diameter D a . This is a simplifying assumption in view of the fact that, in a real acinus, there is a small reduction of the diameter of the airways along successive generations.…”

Section: Mathematical Modelmentioning

confidence: 99%

“…The transport of a gas species in the human acini has been the subject of many previous studies, notably considering 3D complex structures (Felici et al, 2005 ; Hofemeier et al, 2016 ). Here, we use a classical quasi-steady 1D approach, as in several works (Paiva, 1972 , 1973 ; Karamaoun et al, 2016 ; Noel and Mauroy, 2019 ). It is fully described in Appendix 3 .…”

Section: Mathematical Modelmentioning

confidence: 99%

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Modeling of the Transport and Exchange of a Gas Species in Lungs With an Asymmetric Branching Pattern. Application to Nitric Oxide

et al. 2020

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Over the years, various studies have been dedicated to the mathematical modeling of gas transport and exchange in the lungs. Indeed, the access to the distal region of the lungs with direct measurements is limited and, therefore, models are valuable tools to interpret clinical data and to give more insights into the phenomena taking place in the deepest part of the lungs. In this work, a new computational model of the transport and exchange of a gas species in the human lungs is proposed. It includes (i) a method to generate a lung geometry characterized by an asymmetric branching pattern, based on the values of several parameters that have to be given by the model user, and a method to possibly alter this geometry to mimic lung diseases, (ii) the calculation of the gas flow distribution in this geometry during inspiration or expiration (taking into account the increased resistance to the flow in airways where the flow is non-established), (iii) the evaluation of the exchange fluxes of the gaseous species of interest between the tissues composing the lungs and the lumen, and (iv) the computation of the concentration profile of the exchanged species in the lumen of the tracheobronchial tree. Even if the model is developed in a general framework, a particular attention is given to nitric oxide, as it is not only a gas species of clinical interest, but also a gas species that is both produced in the walls of the airways and consumed within the alveolar region of the lungs. First, the model is presented. Then, several features of the model, applied to lung geometry, gas flow and NO exchange and transport, are discussed, compared to existing works and notably used to give new insights into experimental data available in the literature, regarding diseases, such as asthma, cystic fibrosis, and chronic obstructive pulmonary disease.

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Section: Introductionsupporting

confidence: 84%

Section: Mathematical Modelmentioning

confidence: 99%

Section: Mathematical Modelmentioning

confidence: 99%

See 1 more Smart Citation

Modeling of the Transport and Exchange of a Gas Species in Lungs With an Asymmetric Branching Pattern. Application to Nitric Oxide

et al. 2020

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“…First, we use a simplified representation of the lungs, where R i +1 = hR i , with h = 2 −1/3 , and L i / R i = β (independent of i ), as in Mauroy et al ( 2004 ), Noel and Mauroy ( 2019 ), and West et al ( 1997 ). To calculate the number n of generations in the bronchial tree, we assume that this tree stops when the successive divisions have generated airways with a radius smaller than the alveolar diameter, d alv (i.e.,

and

).…”

Section: Mathematical Modelmentioning

confidence: 99%

Comprehensive Analysis of Heat and Water Exchanges in the Human Lungs

et al. 2021

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This work presents a new mathematical model of the heat and water exchanges in the human lungs (newborn to adult). This model is based on a local description of the water and energy transports in both the lumen and the surrounding tissues, and is presented in a comprehensive, dimensionless framework with explicitly stated assumptions and a strong physiological background. The model is first used to analyze and quantify the key phenomena and dimensionless numbers governing these heat and water exchanges and then it is applied to an adult in various situations (varying atmospheric conditions, exercising…). The results highlight several interesting physiological elements. They show that the bronchial region of the lungs is able to condition the air in all the considered situations even if, sometimes, for instance when exercising, distal generations have to be involved. The model also shows that these distal generations are super-conditioners. Moreover, the results quantify the key role of the submucosal glands in mucus hydration. They also show that, during expiration, a significant cooling of the air and condensation of water occur along the respiratory tract as the vascularization of the tissues surrounding the airways is not able to maintain these tissues at body temperature during inspiration. Due to the interaction between several phenomena, it appears that the ratio of the amount of water returned to the mucosa during expiration to the amount extracted during inspiration is almost independent of the breathing conditions (around 33%). The results also show that, in acute situations, such as suffering from a pathology with airway dysfunction, when being intubated or when exercising above an intensity threshold, the heat and water exchanges in the lungs may be critical regarding mucus hydration. In proximal generations, the evaporation may overwhelm the ability of the submucosal glands to replenish the airway surface liquid with water. In some situations, the cooling of the mucosa may be very important; it can even become colder than the inspired air, due to evaporative cooling. Finally, the results show that breathing cold air can significantly increase the exchanges between the lungs and the environment, which can be critical regarding disease transmission.

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“…More recently, Noël and Mauroy (2019) optimized the energy spent for ventilation in humans with a more realistic functional constraint, based on the oxygen flow in the alveoli, including the physics of oxygen and carbon dioxide transport in a symmetric branched model of lung. This approach was not only able to predict physiological ventilation parameters for a wide range of metabolic regimes, but it also highlighted the distribution and transport of oxygen and carbon dioxide in the lung.…”

Section: Introductionmentioning

confidence: 99%

How mammals adapt their breath to body activity – and how this depends on body size

Liebermeister

2021

PCI Math Comp Biol

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A model of optimal control of ventilation has recently been developed for humans. This model highlights the importance of the localization of the transition between a convective and a diffusive transport of respiratory gas. This localization determines how ventilation should be controlled in order to minimize its energetic cost at any metabolic regime. We generalized this model to any mammal, based on the core morphometric characteristics shared by all mammalian lungs and on their allometric scaling from the literature. Since the main energetic costs of ventilation are related to convective transport, we prove that, for all mammals, the localization of the shift from a convective transport to a diffusive transport plays a critical role on keeping this cost low while fulfilling the lung function. Our model predicts for the first time the localization of this transition in order to minimize the energetic cost of ventilation, depending on mammal mass and metabolic regime.From this optimal localization, we are able to predict allometric scaling laws for both tidal volumes and breathing rates, at any metabolic rate. We ran our model for the three common metabolic rates -basal, field and maximal -and showed that our predictions reproduce accurately experimental data available in the literature. Our analysis supports the hypothesis that mammals allometric scaling laws of tidal volumes and breathing rates at a given metabolic rate are driven by a few core geometrical characteristics shared by mammalian lungs and by the physical processes of respiratory gas transport.

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Interplay Between Optimal Ventilation and Gas Transport in a Model of the Human Lung

Cited by 15 publications

References 41 publications

Modeling of the Transport and Exchange of a Gas Species in Lungs With an Asymmetric Branching Pattern. Application to Nitric Oxide

Modeling of the Transport and Exchange of a Gas Species in Lungs With an Asymmetric Branching Pattern. Application to Nitric Oxide

Comprehensive Analysis of Heat and Water Exchanges in the Human Lungs

How mammals adapt their breath to body activity – and how this depends on body size

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