Comparison of generic and subject-specific models for simulation of pulmonary perfusion and forced expiration

Abstract

One contribution of 11 to a theme issue 'Multiscale modelling in biomechanics: theoretical, computational and translational challenges'. The goal of translating multiscale model analysis of pulmonary function into population studies is challenging because of the need to derive a geometric model for each subject. This could be addressed by using a generic model with appropriate customization to subject-specific data. Here, we present a quantitative comparison of simulating two fundamental behaviours of the lung-its haemodynamic response to vascular occlusion, and the forced expiration in 1 s (FEV 1 ) following bronchoconstriction-in subject-specific and generic models. When the subjects are considered as a group, there is no significant difference between predictions of mean pulmonary artery pressure (mPAP), pulmonary vascular resistance or forced expiration; however, significant differences are apparent in the prediction of arterial oxygen, for both baseline and post-occlusion. Despite the apparent consistency of the generic and subject-specific models, a third of subjects had generic model under-prediction of the increase in mPAP following occlusion, and half had the decrease in arterial oxygen over-predicted; two subjects had considerable differences in the percentage reduction of FEV 1 following bronchoconstriction. The generic model approach can be useful for physiologically directed studies but is not appropriate for simulating pathophysiological function that is strongly dependent on interaction with lung structure.

Development and Analysis of Patient-Based Complete Conducting Airways Models

“…The airways resistance calculated here is only one metric of model validity and relevance. A number of three-dimensional models have been used to predict further aspects of lung function and their response to bronchoconstriction, such as regional ventilation distribution [ 12 , 40 , 41 ], FEV1 [ 16 ], the frequency dependence of ventilation [ 42 – 44 ]. Simulating these functional measures using, as a basis, the anatomical models described here would provide a greater understanding of the anatomical models’ validity as patient based models.…”

“…Indeed, given that the generated airways are not truly patient-specific, but only patient-based, it is not clear whether using these models in a patient-specific setting is appropriate. Recent work, using n = 6 subjects, suggests that patient-based models of the type described here are required to accurately model FEV1 [ 16 ]. The study concluded that anatomical model creation is a time consuming process that would have to be streamlined to allow simulations on a large number of subjects.…”

Capturing complexity in pulmonary system modelling

“…to generate airways that are not visible in imaging or to define respiratory parameters that cannot be or have not been measured in the individual). 44,60 This means, for example, that they can be used to relate the spatial location of ventilation defects seen in imaging to local changes in airway resistance. 61 Anatomically based models have also been loosely coupled with models of lung tissue mechanics meaning that local lung tissue deformation and elastic recoil due to gravitational influences are incorporated, 26 allowing predictions of the relative influence of gravity and airway structure to ventilation distribution.…”

Estimation of Lung Properties From the Forced Expiration Data

“…These findings, combined with the morphological model for the symmetrical bronchial tree [6], allowed Lambert and coworkers to elaborate the pioneering, validated, and widely recognized computational model for the descending part of the FV curve [7]. This model was further developed to simulate forced expiration in the whole range of lung vital capacity (VC) [8] and to include the asymmetrical bronchial tree structure [9], [10]. Thereby, the forward problem in spirometry was generally solved.…”