Gas transport during high-frequency ventilation: Theoretical model and experimental validation

W. Mitzner, S. Permutt, G. Weinmann

Research output: Contribution to journalArticlepeer-review

Abstract

We present a theoretical model of gas transport through the dead space during high-frequency ventilation (HFV) with volumes less than dead space volume. The analysis is based on the axial distribution of transit times of gas moving through the dead space. The model predicts that for tidal volumes (V) much less than dead space (Vd), gas exchange will be proportional to the product of frequency (f) and V2. If gas transport is analyzed in terms of Fick's law, then the effective diffusion coefficient (Deff) can be shown to be equal to fV2 times a constant, whose value equals the square of the coefficient of dispersion of axial transit times through the dead space {Mathematical expression}. Experimental results in straight tubes fit the predictions of this model quite well. A {Mathematical expression} through the entire dead space of about 30% is more than sufficient to account for gas exchange during HFV in physical models or in intact animals. An axial dispersion of this magnitude can be measured directly from a typical Fowler dead space determination in healthy subjects.

Original languageEnglish (US)
Pages (from-to)407-419
Number of pages13
JournalAnnals of biomedical engineering
Volume12
Issue number4
DOIs
StatePublished - Jul 1 1984

Keywords

  • Dead space
  • Effective diffusivity
  • Enhanced diffusion
  • Gamma distribution

ASJC Scopus subject areas

  • Biomedical Engineering

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