1. HFOV Mechanisms of Gas Transport

2. HFOV Mechanisms of Gas Transport
Direct bulk flow
Taylor dispersion
Pendeluft
Asymmetric velocity profiles
Cardiogenic mixing
Molecular diffusion
Krishnan CHEST 2000

3. 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.

4. Augmented (Taylor) dispersion
Complicated interplay between convective forces and molecular diffusion
Addition of convective flow to a diffusive process significantly increased dispersion of molecules

5. 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.

6. Asymmetrical Velocity Profile
Inspiration
Net Effect
Expiration

7. Cardiogenic Mixing
The heart beat adds to the the peripheral gas mixing.

8. 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.