## 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 (V_{d}), gas exchange will be proportional to the product of frequency (f) and V^{2}. If gas transport is analyzed in terms of Fick's law, then the effective diffusion coefficient (D_{eff}) can be shown to be equal to fV^{2} 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 language | English (US) |
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Pages (from-to) | 407-419 |

Number of pages | 13 |

Journal | Annals of biomedical engineering |

Volume | 12 |

Issue number | 4 |

DOIs | |

State | Published - Jul 1 1984 |

## Keywords

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

## ASJC Scopus subject areas

- Biomedical Engineering