hfov mechanisms of gas transport. viasys healthcare, inc. 1.direct bulk flow 2.taylor dispersion...
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![Page 1: HFOV Mechanisms of Gas Transport. VIASYS Healthcare, Inc. 1.Direct bulk flow 2.Taylor dispersion 3.Pendeluft 4.Asymmetric velocity profiles 5.Cardiogenic](https://reader036.vdocuments.site/reader036/viewer/2022081700/56649ea85503460f94bac850/html5/thumbnails/1.jpg)
HFOV Mechanisms of Gas Transport
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VIASYS Healthcare, Inc.
1. Direct bulk flow
2. Taylor dispersion
3. Pendeluft
4. Asymmetric velocity profiles
5. Cardiogenic mixing
6. Molecular diffusion
HFOV Mechanisms of Gas Transport
Krishnan CHEST 2000
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VIASYS Healthcare, Inc.
Convection (Bulk Flow) Ventilation
• Even with small tidal volumes, direct alveolar ventilation occurs to short path length units that branch off of the primary airways.
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VIASYS Healthcare, Inc.
Augmented (Taylor) dispersion
• Complicated interplay between convective forces and molecular diffusion
• Addition of convective flow to a diffusive process significantly increased dispersion of molecules
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VIASYS Healthcare, Inc.
Penduluft
• At high frequencies, distribution becomes strongly influenced by time constant inequalities. Gas from fast units (short time constants) will empty into the slow (long time constants) units.
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VIASYS Healthcare, Inc.
Asymmetrical Velocity Profile
Inspiration
Net Effect
Expiration
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VIASYS Healthcare, Inc.
Cardiogenic Mixing
• The heart beat adds to the the peripheral gas mixing.
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VIASYS Healthcare, Inc.
Molecular Diffusion
• Is felt to be one of the major mechanisms for gas exchange in the alveolar regions.
• It is responsible for the gas exchange across the AC membrane and also contributes to the transport of O2 and CO2 in the gas phase near the membrane.
• This may be due to the increased turbulence of molecules.