Geometric hysteresis of alveolated ductal architecture

M. Kojic, J. P. Butler, I. Vlastelica, B. Stojanovic, V. Rankovic, A. Tsuda

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Low Reynolds number airflow in the pulmonary acinus and aerosol particle kinetics therein are significantly conditioned by the nature of the tidal motion of alveolar duct geometry. At least two components of the ductal structure are known to exhibit stress-strain hysteresis: smooth muscle within the alveolar entrance rings, and surfactant at the air-tissue interface. We hypothesize that the geometric hysteresis of the alveolar duct is largely determined by the interaction of the amount of smooth muscle and connective tissue in ductal rings, septal tissue properties, and surface tension-surface area characteristics of surfactant. To test this hypothesis, we have extended the well-known structural model of the alveolar duct by Wilson and Bachofen (1982, A Model for Mechanical Structure of the Alveolar Duct, J. Appl. Physiol. 52(4), pp. 1064-1070) by adding realistic elastic and hysteretic properties of (1) the alveolar entrance ring, (2) septal tissue, and (3) surfactant. With realistic values for tissue and surface properties, we conclude that: (1) there is a significant, and underappreciated, amount of geometric hysteresis in alveolar ductal architecture; and (2) the contribution of smooth muscle and surfactant to geometric hysteresis are of opposite senses, tending toward cancellation. Quantitatively, the geometric hysteresis found experimentally by Miki (1993, Geometric Hysteresis in Pulmonary Surface-to-Volume Ratio during Tidal Breathing, J. Appl. Physiol. 75(4), pp. 1630-1636) is consistent with little or no smooth muscle tone in anesthetized rabbits in control conditions, and with substantial smooth muscle activation following methacholine challenge. The observed local hysteretic boundary motion of the acinar duct would result in irreversible acinar flow fields, which might be important mechanistic contributors to aerosol mixing and deposition deep in the lung.

Original languageEnglish (US)
Article number111005
JournalJournal of Biomechanical Engineering
Volume133
Issue number11
DOIs
StatePublished - 2011

Keywords

  • acinar kinematic irreversibility
  • connective tissue
  • finite element model
  • geometric hysteresis
  • lung
  • micromechanics
  • smooth muscle
  • surfactant

ASJC Scopus subject areas

  • Biomedical Engineering
  • Physiology (medical)

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