EditorialMultiscale Computational Models for Respiratory AerosolDynamics with Medical Applications

Yu Feng ,1 Xiaole Chen,2 Mingshi Yang,3 and Ke-jun Dong4

1School of Chemical Engineering, Oklahoma State University, Stillwater, Oklahoma, USA2School of Energy and Environment, Southeast University, Nanjing, Jiangsu, China3Department of Pharmacy, University of Copenhagen, Copenhagen, Denmark4Centre for Infrastructure Engineering, Western Sydney University, Penrith, Australia

Correspondence should be addressed to Yu Feng; yu.feng@okstate.edu

Received 10 February 2019; Accepted 10 February 2019; Published 3 March 2019

Copyright © 2019 Yu Feng et al."is is an open access article distributed under the Creative Commons Attribution License, whichpermits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1. Introduction

Inhalation of therapeutic drug aerosols is now becoming anovel way to administer micro/nanoparticles or vapors totreat lung and systemic diseases. Several attempts of suchdeliveries have been made at least in experimental analyseson asthma, chronic obstructive pulmonary disease (COPD),lung hypoxia, edema, lung injury, lung transplantationfungal infection, pulmonary fibrosis, and lung cancer.However, due to certain design deficiencies, existing pul-monary drug delivery devices still have poor efficiencies fordelivering drugs to designated sites. Significant portions ofthe aggressive medicine deposit on healthy tissues, whichcauses severe side effects and induces extra healthcare ex-penses. "erefore, it is an urgent need to understand theaerosol drug dynamics better and develop a revolutionarypatient-specific pulmonary drug delivery method and deviceto improve therapeutic outcomes by significantly improvingdrug delivery efficacy significantly. Due to the invasivenature and imaging resolution limitations, clinical andanimal studies are not able to provide the high-resolutiondata for the researcher to understand the particle dynamicsin human lung airways. Compared to experimental in-vestigations, accurate and realistic computer simulationmodels would significantly contribute to reducing the re-search time and cost and visualize drug transport andtranslocation to multiple health endpoints via the pulmo-nary route.

To pave the way to developing the next-generationcomputational model and advance the scientific knowledge

of respiratory aerosol dynamics, this special issue covers awide range of multiscale computational models with differentmedical applications. Seven exciting papers are included, andthey might be broadly categorized into three levels: (a) re-spiratory system level, (b) cell level, and (c) disease level.

2. Overview of the Works Published in ThisSpecial Issue

2.1. Respiratory System Level. "e focus of the first groupwhich consists of 3 papers, which advance the fundamentalunderstanding on how to more realistically model the in-haled aerosol transport and deposition in human respiratorysystems and how different physiological factors can influ-ence the deposition patterns. "ese factors include preex-isting lung disease conditions, alveolar movements,breathing patterns, and aerosol size distributions. Specifi-cally, A. V. Kolanjiyil and C. Kleinstreuer created an elastic“whole acinar model” which covers the entire alveolateddistal airways and alveolar sacs and simulates particletransport and deposition via CFPD coupled with the fluid-structure interaction (FSI) method. "eir results indicatethat the alveolar wall motion significantly increases particledeposition, and particle deposition efficiency increases withhigher inhalation tidal volume and aerosol size. "e acinarmodel can efficiently simulate aerosol dynamics in the deeplung and is ready to be incorporated into the next-generationwhole-lung model. Also, focusing on the aerosol dynamicsin alveolar regions, J. Xi et al. investigated the impact ofKohn structures on particle depositions in their elastic

HindawiComputational and Mathematical Methods in MedicineVolume 2019, Article ID 4304139, 2 pageshttps://doi.org/10.1155/2019/4304139

alveolar models for both healthy people and emphysemapatients. Temporal and spatial deposition variations inmultialveoli pore-communicated acinar models were nu-merically simulated. "ey found the size of the pores ofKohn, inhalation depth, and gravity orientation angle hadinsignificant effects on acinar deposition but had dramaticimpact on the spatial distribution of particle depositionamong alveoli. Furthermore, S. Choi et al. also used theCFPD-based model and explored the effect of alteredstructures and functions in severe asthma on particle de-position in subject-specific human respiratory systems. CFDresults show that the induced constricted airways by asthmacontribute to high wall shear stress, elevated pressure drop,and significantly increased particle deposition, compared tonormal airways of healthy people.

2.2. Disease Level. "e second group consists of 2 paperswhich developed mathematical models to investigate thetransmission and control of infectious disease caused byinhalable bioaerosols (e.g., bacteria and virus). F. Li et al.investigated the infectious disease, e.g., the severe acuterespiratory syndrome (SARS), via a stochastic susceptible-exposed-infected-quarantined-recovered (SEIQR) epidemicmodel with quarantine-adjusted incidence and the imperfectvaccination. "eir theoretical analysis and simulations showthat the stochastic disturbance is conducive to epidemicdiseases control. K. Liu et al. analyzed the system dynamicsof the state-dependent pulse vaccination and therapeuticstrategy, which is described based on an SI ordinary dif-ferential equationmodel."eir results indicate that the state-dependent impulsive vaccination strategy could be used as asupplementary approach or under the situation when vac-cine stockpile is limited.

2.3. Cell Level. "e third group also consists of 2 papers,modeling transport and reproduction of cells. Y. Ji et al.studied the virus infection dynamics using a mathematicalmodel. "is model included a time delay term standing forthe growth of the uninfected cells."emathematical analysisindicates that the growth of the uninfected cells can com-plicate the infection results, e.g., relapse of the infection.From the biological aspect, it suggests that adequate drugtreatment should be employed to avoid relapse or oscillationin the immune response. R. Wang et al. examined thetransport and deformation of red blood cells throughconstricted microchannels using the immersed boundary-lattice Boltzmann method. "eir simulations found thatgreater deformation and longer travel time were required tosqueeze through the narrower channel.

3. Conclusions

"is special issue documents some new studies and providesstate-of-art advanced multiscale numerical modeling effortsfor respiratory aerosol dynamics in pulmonary drug deliverydevice, human respiratory systems, and systemic regions, aswell as other induced kinetics and dynamics in the humanbody. "e accepted papers show a diversity of new findings

and overviews of the recent research and development. Wehope this special issue will foster a wider interest in findingthe most feasible way for the development of the next-generation multiscale model, to bring the computationalrespiratory aerosol dynamics simulations to health end-points with the details never undertaken before in the nearfuture.

Conflicts of Interest

Editors report no conflicts of interest in this work.

Acknowledgments

"e editors are grateful to the participants of this specialissue for their inspiring contributions and the anonymousreviewers for their helpful and constructive comments whichgreatly improved the content of the papers published in thisspecial issue.

Yu FengXiaole Chen

Mingshi YangKe-jun Dong

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