Viscosity and density of common anaesthetic gases: implications for flow measurements

Habre, W., Asztalos, T., Sly, P.D. and Petak, F. (2001) Viscosity and density of common anaesthetic gases: implications for flow measurements. British Journal of Anaesthesia, 87 4: 602-607. doi:10.1093/bja/87.4.602

Author Habre, W.
Asztalos, T.
Sly, P.D.
Petak, F.
Title Viscosity and density of common anaesthetic gases: implications for flow measurements
Journal name British Journal of Anaesthesia   Check publisher's open access policy
ISSN 0007-0912
Publication date 2001-10
Sub-type Article (original research)
DOI 10.1093/bja/87.4.602
Volume 87
Issue 4
Start page 602
End page 607
Total pages 6
Place of publication Oxford, United Kingdom
Publisher Oxford University Press
Language eng
Abstract Although viscosity (μ) is a crucial factor in measurements of flow with a pneumotachograph, and density (ρ) also plays a role in the presence of turbulent flow, these material constants are not available for the volatile anaesthetic agents commonly administered in clinical practice. Thus, we determined experimentally μ and ρ of pure volatile anaesthetic agents. Input impedance of a rigid-wall polyethylene tube (Zt) was measured when the tube was filled with various mixtures of carrier gases (air, 100% oxygen, 50% oxygen+50% nitrogen) to which different concentrations of volatile anaesthetic inhalation agents (halothane, isoflurane, sevoflurane, and desflurane) had been added. μ and ρ were calculated from real and imaginary portions of Zt, respectively, using the appropriate physical equations. Multiple linear regression was applied to estimate μ and ρ of pure volatile agents. Viscosity values of pure volatile agents were markedly lower than those for oxygen or nitrogen. Clinically applied concentrations, however, did not markedly affect the viscosity of the gas mixture (maximum of 3.5% decrease in μ for 2 MAC desflurane). In contrast, all of the volatile agents significantly affected ρ even at routinely used concentrations. Our results suggest that the composition of the carrier gas has a greater impact on viscosity than the amount and nature of the volatile anaesthetic agent whereas density is more influenced by volatile agent concentrations. Thus, the need for a correction factor in flow measurements with a pneumotachograph depends far more on the carrier gas than the concentration of volatile agent administered, although the latter may play a role in particular experimental or clinical settings.
Keyword Anaesthetic techniques
Measurement techniques, pneumotachograph
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Medicine Publications
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Citation counts: TR Web of Science Citation Count  Cited 9 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 11 times in Scopus Article | Citations
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Created: Wed, 17 Nov 2010, 11:27:54 EST