Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/42997
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Type: Journal article
Title: Perfusion-diffusion compartmental models describe cerebral helium kinetics at high and low cerebral blood flows in sheep
Author: Doolette, D.
Upton, R.
Grant, C.
Citation: Journal of Physiology-London, 2005; 563(2):529-539
Publisher: Blackwell Publishing Ltd
Issue Date: 2005
ISSN: 0022-3751
1469-7793
Statement of
Responsibility: 
David J Doolette, Richard N Upton and Cliff Grant
Abstract: This study evaluated the relative importance of perfusion and diffusion mechanisms in compartmental models of blood:tissue helium exchange in the brain. Helium has different physiochemical properties from previously studied gases, and is a common diluent gas in underwater diving where decompression schedules are based on theoretical models of inert gas kinetics. Helium kinetics across the cerebrum were determined during and after 15 min of helium inhalation, at separate low and high steady states of cerebral blood flow in seven sheep under isoflurane anaesthesia. Helium concentrations in arterial and sagittal sinus venous blood were determined using gas chromatographic analysis, and sagittal sinus blood flow was monitored continuously. Parameters and model selection criteria of various perfusion-limited or perfusion–diffusion compartmental models of the brain were estimated by simultaneous fitting of the models to the sagittal sinus helium concentrations for both blood flow states. Purely perfusion-limited models fitted the data poorly. Models that allowed a diffusion-limited exchange of helium between a perfusion-limited tissue compartment and an unperfused deep compartment provided better overall fit of the data and credible parameter estimates. Fit to the data was also improved by allowing countercurrent diffusion shunt of helium between arterial and venous blood. These results suggest a role of diffusion in blood:tissue helium equilibration in brain.
Keywords: Brain; Animals; Sheep; Helium; Diffusion; Tissue Distribution; Cerebrovascular Circulation; Solubility; Models, Biological; Female
RMID: 0020077054
DOI: 10.1113/jphysiol.2004.077842
Appears in Collections:Anaesthesia and Intensive Care publications

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