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research-article

In vivo dynamics of the tracheal airway and its influences on respiratory airflows

[+] Author and Article Information
Bora Sul

The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, Maryland; Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Materiel Command, Fort Detrick, Maryland
bsul@bhsai.org

Talissa Altes

Department of Radiology, University of Missouri, Columbia, Missouri
altest@health.missouri.edu

Kai Ruppert

Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
kai.ruppert@gmail.com

Kun Qing

Department of Radiology, University of Virginia, Charlottesville, Virginia
kq4d@virginia.edu

Daniel S Hariprasad

The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, Maryland; Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Materiel Command, Fort Detrick, Maryland
dhariprasad@bhsai.org

Michael Morris

Graduate Medical Education, Brooke Army Medical Center, Joint Base San Antonio Fort Sam Houston, Texas
michael.j.morris34.civ@mail.mil

Jaques Reifman

Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Materiel Command, Fort Detrick, Maryland
jaques.reifman.civ@mail.mil

Anders Wallqvist

Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Materiel Command, Fort Detrick, Maryland
sven.a.wallqvist.civ@mail.mil

1Corresponding author.

ASME doi:10.1115/1.4043723 History: Received January 31, 2019; Revised May 01, 2019

Abstract

Respiration is a dynamic process accompanied by morphological changes in the airways. Although deformation of large airways is expected to exacerbate pulmonary disease symptoms by obstructing airflow during increased minute ventilation, its quantitative effects on airflow characteristics remain unclear. Here, we used an exemplar case derived from in vivo dynamic imaging and examined the effects of tracheal deformation on airflow characteristics under different conditions. First, we measured tracheal deformation profiles of a healthy lung using magnetic resonance imaging during forced exhalation, which we simulated to characterize subject-specific airflow patterns. Subsequently, for both inhalation and exhalation, we compared the airflows when the maximal deformation in tracheal cross-sectional area was 0% (rigid), 33% (mild), 50% (moderate), or 75% (severe). We quantified differences in airflow patterns between deformable and rigid airways by computing the correlation coefficients (R) and the root-mean-square of differences (Drms) between their velocity contours. For both inhalation and exhalation, airflow patterns were similar in all branches between the rigid and mild conditions (R > 0.9; Drms < 32%). However, airflow characteristics in the moderate and severe conditions differed markedly from those in the rigid and mild conditions in all lung branches, particularly for inhalation (moderate: R > 0.1, Drms < 76%; severe: R > 0.2, Drms < 96%). Our exemplar case supports the use of a rigid airway assumption to compute flows for mild deformation. For moderate or severe deformation, however, dynamic contraction should be considered, especially during inhalation, to accurately predict airflow and elucidate the underlying pulmonary pathology.

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