Coupled and reduced dimensional modeling of respiratory mechanics during spontaneous breathing

Abstract

In this paper, we develop a total lung model based on a tree of 0D airway and acinar models for studying respiratory mechanics during spontaneous breathing. This model utilizes both computer tomography-based geometries and artificially generated lobe-filling airway trees to model the entire conducting region of the lung. Beyond the conducting airways, we develop an acinar model, which takes into account the alveolar tissue resistance, compliance, and the intrapleural pressure. With this methodology, we compare four different 0D models of airway mechanics and determine the best model based on a comparison with a 3D-0D coupled model of the conducting airways; this methodology is possible because the majority of airway resistance is confined to the lower generations, that is, the trachea and the first few bronchial generations. As an example application of the model, we simulate the flow and pressure dynamics under spontaneous breathing conditions, that is, at flow conditions driven purely by pleural space pressure. The results show good agreement, both qualitatively and quantitatively, with reported physiological values. One of the key advantages of this model is the ability to provide insight into lung ventilation in the peripheral regions. This is often crucial because this is where information, specifically for studying diseases and gas exchange, is needed. Thus, the model can be used as a tool for better understanding local peripheral lung mechanics without excluding the upper portions of the lung. This tool will be also useful for in vitro investigations of lung mechanics in both health and disease.

A poroelastic model coupled to a fluid network with applications in lung modelling

“…Incompressibility To further simplify the poroelastic equations we assume that both the solid phase (blood and tissue) and a fluid phase (air) are incompressible [1].…”

“…Mixture theory, also known as the Theory of Porous Media (TPM) [23,24,2], has its roots in the classical theories of gas mixtures and makes use of a volume fraction concept in which the porous medium is represented by spatially superposed interacting media. An alternative, purely macroscopic approach is mainly associated with the work of Biot, and a detailed description can be found in the book by Coussy [1]. Relationships between the two theories are explored in [25,26].…”

“…In this work, we focus on the link between tissue deformation and ventilation. Previous work of whole organ lung models has typically focused on modelling either ventilation or tissue deformation [1,2,3,4,5,6,7,8]. However, the two components are intrinsically linked; evaluating them separately does not necessarily provide an accurate description of lung function.…”

“…Ventilation models that incorporate many independent elastic alveolar units, e.g., [1,2] are commonly known as balloon models. In these models, alveolar units can expand and contract independently of the sizes and positions of neighbouring units, which can lead to unphysical solutions in which multiple balloons apparently occupy the same location in space.…”

“…Lung models [1,2] provide information regarding the distribution of flow within the lung as a result of a pleural pressure boundary condition. However it is not possible to experimentally measure the pleural pressure in vivo using imaging or other apparatus.…”