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J Breath Res

Title:		A modeling-based evaluation of isothermal rebreathing for breath gas analyses of highly soluble volatile organic compounds
Author(s):		King J; Unterkofler K; Teschl G; Teschl S; Mochalski P; Koc H; Hinterhuber H; Amann A;
Address:		"Breath Research Institute, Austrian Academy of Sciences, Dornbirn, Austria"
Journal Title:		J Breath Res
Year:		2012
Volume:		20120110
Issue:		1
Page Number:		16005 -
DOI:		10.1088/1752-7155/6/1/016005
ISSN/ISBN:		1752-7163 (Electronic) 1752-7155 (Linking)
Abstract:		"Isothermal rebreathing has been proposed as an experimental technique for estimating the alveolar levels of hydrophilic volatile organic compounds (VOCs) in exhaled breath. Using the prototypic test compounds acetone and methanol, we demonstrate that the end-tidal breath profiles of such substances during isothermal rebreathing show a characteristic increase that contradicts the conventional pulmonary inert gas elimination theory due to Farhi. On the other hand, these profiles can reliably be captured by virtue of a previously developed mathematical model for the general exhalation kinetics of highly soluble, blood-borne VOCs, which explicitly takes into account airway gas exchange as a major determinant of the observable breath output. This model allows for a mechanistic analysis of various rebreathing protocols suggested in the literature. In particular, it predicts that the end-exhaled levels of acetone and methanol measured during free tidal breathing will underestimate the underlying alveolar concentration by a factor of up to 1.5. Moreover, it clarifies the discrepancies between in vitro and in vivo blood-breath ratios of hydrophilic VOCs and yields further quantitative insights into the physiological components of isothermal rebreathing and highly soluble gas exchange in general"
Keywords:		Acetone/*analysis Adult Breath Tests/*methods Exhalation Humans Lung/*chemistry Male Methanol/*analysis Middle Aged *Pulmonary Gas Exchange Respiration Spirometry Volatile Organic Compounds/*analysis;
Notes:		"MedlineKing, J Unterkofler, K Teschl, G Teschl, S Mochalski, P Koc, H Hinterhuber, H Amann, A eng Research Support, Non-U.S. Gov't England 2012/01/12 J Breath Res. 2012 Mar; 6(1):016005. doi: 10.1088/1752-7155/6/1/016005. Epub 2012 Jan 10"