Morphological and functional properties of the conducting human airways investigated by in vivo computed tomography and in vitro MRI

Tristan Van De Moortele, Christine H. Wendt, Filippo Coletti

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

The accurate representation of the human airway anatomy is crucial for understanding and modeling the structure-function relationship in both healthy and diseased lungs. The present knowledge in this area is based on morphometric studies of excised lung casts, partially complemented by in vivo studies in which computed tomography (CT) was used on a small number of subjects. In the present study, we analyzed CT scans of a cohort of healthy subjects and obtained comprehensive morphometric information down to the seventh generation of bronchial branching, including airway diameter, length, branching angle, and rotation angle. Although some of the geometric parameters (such as the child-to-parent branch diameter ratio) are found to be in line with accepted values, for others (such as the branch length-to-diameter ratio) our findings challenge the common assumptions. We also evaluated several metrics of self-similarity, including the fractal dimension of the airway tree. Additionally, we used phase-contrast magnetic resonance imaging (MRI) to obtain the volumetric flow field in the three-dimensional-printed airway model of one of the subjects during steady inhalation. This is used to relate structural and functional parameters and, in particular, to close the power-law relationship between branch flow rate and diameter. The diameter exponent is found to be significantly lower than in the usually assumed Poiseuille regime, which we attribute to the strong secondary (i.e., transverse) velocity component. The strength of the secondary velocity with respect to the axial component exceeds the levels found in idealized airway models and persists within the first seven generations.

Original languageEnglish (US)
Pages (from-to)400-413
Number of pages14
JournalJournal of applied physiology
Volume124
Issue number2
DOIs
StatePublished - Feb 2018

Bibliographical note

Funding Information:
Funding for this work was provided by the National Science Foundation (CBET-1453538) and the National Heart, Lung, and Blood Institute (Grant R21-HL-129906). COPDGene was supported by Awards R01-HL-089897 and R01-HL-089856 from the National Heart, Lung, and Blood Institute and by the COPD Foundation through contributions made to an Industry Advisory Board composed of AstraZeneca, Boehringer Ingelheim, GlaxoSmithKline, Novartis, Pfizer, Siemens, and Sunovion.

Publisher Copyright:
Copyright © 2018 American Physiological Society. All rights reserved.

Keywords

  • Airway morphometry
  • Computed tomography
  • Magnetic resonance imaging
  • Structure-function relationship

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