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The mechanism of breath aerosol formation

Johnson, Graham R. & Morawska, Lidia (2009) The mechanism of breath aerosol formation. Journal of Aerosol Medicine and Pulmonary Drug Delivery, 22(3), pp. 229-237.

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Abstract

Background: Aerosol production during normal breathing is often attributed to turbulence in the respiratory tract. That mechanism is not consistent with a high degree of asymmetry between aerosol production during inhalation and exhalation. The objective was to investigate production symmetry during breathing.

Methods: The aerosol size distribution in exhaled breath was examined for different breathing patterns including normal breathing, varied breath holding periods and contrasting inhalation and exhalation rates. The aerosol droplet size distribution measured in the exhaled breath was examined in real time using an aerodynamic particle sizer.

Results and Conclusions: The dependence of the particle concentration decay rate on diameter during breath holding was consistent with gravitational settling in the alveolar spaces. Also, deep exhalation resulted in a 4 to 6 fold increase in concentration and rapid inhalation produced a further 2 to 3 fold increase in concentration. In contrast rapid exhalation had little effect on the measured concentration. A positive correlation of the breath aerosol concentration with subject age was observed.

The results were consistent with the breath aerosol being produced through fluid film rupture in the respiratory bronchioles in the early stages of inhalation and the resulting aerosol being drawn into the alveoli and held before exhalation. The observed asymmetry of production in the breathing cycle with very little aerosol being produced during exhalation, is inconsistent with the widely assumed turbulence induced aerosolization mechanism.

Impact and interest:

36 citations in Scopus
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32 citations in Web of Science®

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ID Code: 27535
Item Type: Journal Article
Keywords: Aerosol Distribution, Exhaled Aerosol, Bronchiole, Physiology, Breath Condensate
DOI: 10.1089/jamp.2008.0720
ISSN: 1941-2703
Subjects: Australian and New Zealand Standard Research Classification > EARTH SCIENCES (040000) > ATMOSPHERIC SCIENCES (040100) > Atmospheric Aerosols (040101)
Australian and New Zealand Standard Research Classification > PHYSICAL SCIENCES (020000) > OTHER PHYSICAL SCIENCES (029900) > Biological Physics (029901)
Divisions: Past > QUT Faculties & Divisions > Faculty of Science and Technology
Current > Institutes > Institute of Health and Biomedical Innovation
Copyright Owner: Copyright 2009 Mary Ann Liebert, Inc. Publishers
Deposited On: 24 Sep 2009 14:25
Last Modified: 01 Mar 2012 00:07

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