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Chaotic mixing deep in the lung.

Authors
  • Tsuda, Akira
  • Rogers, Rick A
  • Hydon, Peter E
  • Butler, James P
Type
Published Article
Journal
Proceedings of the National Academy of Sciences of the United States of America
Publication Date
Jul 23, 2002
Volume
99
Issue
15
Pages
10173–10178
Identifiers
PMID: 12119385
Source
Medline
License
Unknown

Abstract

Our current understanding of the transport and deposition of aerosols (viruses, bacteria, air pollutants, aerosolized drugs) deep in the lung has been grounded in dispersive theories based on untested assumptions about the nature of acinar airflow fields. Traditionally, these have been taken to be simple and kinematically reversible. In this article, we apply the recently discovered fluid mechanical phenomenon of irreversible low-Reynolds number flow to the lung. We demonstrate, through flow visualization studies in rhythmically ventilated rat lungs, that such a foundation is false, and that chaotic mixing may be key to aerosol transport. We found substantial alveolar flow irreversibility with stretched and folded fractal patterns, which lead to a sudden increase in mixing. These findings support our theory that chaotic alveolar flow--characterized by stagnation saddle points associated with alveolar vortices--governs gas kinematics in the lung periphery, and hence the transport, mixing, and ultimately the deposition of fine aerosols. This mechanism calls for a rethinking of the relationship of exposure and deposition of fine inhaled particles.

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