In silico prototype of a human lung with a single airway to predict particle deposition

Abstract

Background Experimental analyses of the flow of drug particles inside the human lung usually require that the patient be exposed to radiation and also of expensive equipment that often lack of enough accuracy. Numerical calculations based on CFD (computational fluid dynamics) have been proven to be a valuable tool to analyze flows in diverse applications. Methods The complexity of the human lung disallows running calculations on complete lung models due to the large number of cells that would be required. In this work, using a proprietary methodology, particle deposition in the lung is simulated by reducing its multiple branches to a single path. Results The tested flow rates were 18, 30, and 75 L min−1, which are equivalent to different respiratory rates varying from light activity to heavy exercise. Most of the particles are accumulated in the upper airways, mainly at the mouth and also at the confluence of the larynx and the trachea (epiglottis), while the remaining particles travel across the lung. The reported procedure allowed simulating the operation of the entire lung by means of a single individual path. Conclusions The obtained calculations are in good agreement with the experimental results found in the technical literature, thus showing that the model can provide a realistic description of the lung operation, while avoiding high computational costs. Moreover, the calculations suggest that particle sizes above 15 μm and inspiratory flows higher than 30 L min−1 must be avoided in order to allow drug particles to reach the lower airways.

Algebraic approximation of the distributed model for the pressure drop in the respiratory airways

“…However, the most commonly used simplification is the adoption of rigid airway walls. 39,47,61 While this enables the simulation of dynamic flows in the 3D od quasi-3D patient-specific structures of the bronchial tree by means of computational fluid dynamics (CFD), 7,9,12,13,[29][30][31][32][33][34][35]36,[51][52][53][54][55][56][57] it does not take into account the aforementioned changes in the bronchial properties caused by variations in pressures and flow, or the associated lung volume. This disadvantage is not present in simulations using fluid-structure interactions (FSI) that allow for the 3D geometry and flexibility of the bronchi to be taken into account.…”

“…Due to this complexity, the infeasibility of direct internal measurements and the nonlinear and dynamic phenomena occurring during breathing, one of the most important approaches to the study on the respiratory system is computational modeling enabling simulations. A variety of models have been used to simulate and analyze respiratory phenomena in both health and disease, for normal breathing [7][8][9][10][11][12][13] as well as mimicking basic diagnostic or lung function supporting modalities, such as forced expiration in spirometry, 4,[14][15][16][17] forced oscillation technique (FOT), [18][19][20][21][22] interrupter technique (IT), 23,24 multi-breath washout, [25][26][27][28] aerosol particle deposition, [29][30][31][32][33][34][35][36] or mechanical ventilation. [37][38][39][40][41][42][43] Those studies have proved the importance and usefulness of respiratory system modeling.…”

“…To handle the discussed complexity of the respiratory system and long computation time when implementing the adequate models, specific simplifications have been adopted so far as the only solution to this problem. By giving only examples of models representing different applications, first of all, the bronchial tree structure followed the Horsfield asymmetric model, 17,41,34 simpler symmetrical Weibel model, 13,22,33,35,37,47 or just structures with a few lumped parameters, usually resistances, compliances and inertances. 19,20,24,28,42,[48][49][50] Moreover, even using the morphology-based models, their structure was kept only for the first generations of conducting airways with combined or omitted smaller bronchioli, [10][11][12][13]16,17,32,37,21,28,48,49,51 or alternatively the acinar region was only taken into account.…”

“…19,20,24,28,42,[48][49][50] Moreover, even using the morphology-based models, their structure was kept only for the first generations of conducting airways with combined or omitted smaller bronchioli, [10][11][12][13]16,17,32,37,21,28,48,49,51 or alternatively the acinar region was only taken into account. 27 The second type of simplifications was based on the assumption of rigid walls of the airways, 13,32,33,35,47,48,[51][52][53][54][55] analyzing the system for a single lung volume or constant flow. 10,19,21,53,55,58 Among these approaches, the quasi-3D model using plenty of wires to simplify fluid dynamics simulations, 56 has proved particularly successful.…”

A revision of the multiple‐path particle dosimetry model focusing on tobacco product aerosol dynamics

“…Computational modeling is a common approach for simulating the deposition and uptake amount in animal and human airways. [6][7][8][9] These days, simulated dosimetry is practically employed for toxicological assessment. For example, the Organization for Economic Co-operation and Development (OECD) showed a case study in which human equivalent concentration was estimated by calculation based on computational fluid dynamics (CFD) modeling.…”