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J Biomech Eng. 2019 May 10. doi: 10.1115/1.4043723. [Epub ahead of print]

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

Author information

1
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.
2
Department of Radiology, University of Missouri, Columbia, Missouri.
3
Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania.
4
Department of Radiology, University of Virginia, Charlottesville, Virginia.
5
Graduate Medical Education, Brooke Army Medical Center, Joint Base San Antonio Fort Sam Houston, Texas.
6
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.

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.

PMID:
31074759
DOI:
10.1115/1.4043723

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