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Altering blood flow does not reveal differences between nitrogen and helium kinetics in brain or in skeletal miracle in sheep.
- Source :
-
Journal of applied physiology (Bethesda, Md. : 1985) [J Appl Physiol (1985)] 2015 Mar 01; Vol. 118 (5), pp. 586-94. Date of Electronic Publication: 2014 Dec 18. - Publication Year :
- 2015
-
Abstract
- In underwater diving, decompression schedules are based on compartmental models of nitrogen and helium tissue kinetics. However, these models are not based on direct measurements of nitrogen and helium kinetics. In isoflurane-anesthetized sheep, nitrogen and helium kinetics in the hind limb (n = 5) and brain (n = 5) were determined during helium-oxygen breathing and after return to nitrogen-oxygen breathing. Nitrogen and helium concentrations in arterial, femoral vein, and sagittal sinus blood samples were determined using headspace gas chromatography, and venous blood flows were monitored continuously using ultrasonic Doppler. The experiment was repeated at different states of hind limb blood flow and cerebral blood flow. Using arterial blood gas concentrations and blood flows as input, parameters and model selection criteria of various compartmental models of hind limb and brain were estimated by fitting to the observed venous gas concentrations. In both the hind limb and brain, nitrogen and helium kinetics were best fit by models with multiexponential kinetics. In the brain, there were no differences in nitrogen and helium kinetics. Hind limb models fit separately to the two gases indicated that nitrogen kinetics were slightly faster than helium, but models with the same kinetics for both gases fit the data well. In the hind limb and brain, the blood:tissue exchange of nitrogen is similar to that of helium. On the basis of these results, it is inappropriate to assign substantially different time constants for nitrogen and helium in all compartments in decompression algorithms.<br /> (Copyright © 2015 the American Physiological Society.)
- Subjects :
- Algorithms
Animals
Cerebrovascular Circulation physiology
Decompression
Decompression Sickness metabolism
Decompression Sickness physiopathology
Diffusion
Diving physiology
Gases metabolism
Hindlimb metabolism
Hindlimb physiology
Kinetics
Models, Biological
Models, Theoretical
Oxygen metabolism
Respiration
Sheep
Brain metabolism
Brain physiology
Helium metabolism
Musculoskeletal System metabolism
Musculoskeletal System physiopathology
Nitrogen metabolism
Regional Blood Flow physiology
Subjects
Details
- Language :
- English
- ISSN :
- 1522-1601
- Volume :
- 118
- Issue :
- 5
- Database :
- MEDLINE
- Journal :
- Journal of applied physiology (Bethesda, Md. : 1985)
- Publication Type :
- Academic Journal
- Accession number :
- 25525213
- Full Text :
- https://doi.org/10.1152/japplphysiol.00944.2014