### Abstract

Although distribution of ventilation may be assessed by both N_{2} washout (NW) and frequency dependence of lung compliance [C(L)] the mathematical link between these tests has not been established. In a mechanical lung model consisting of two compartments of equal volume but variable time constants, alveolar dilution factors for N_{2} (w) were measured at different cycling frequencies. Using equations relating time constants of the model to expected compartmental NW, a good experimental fit was obtained. As two compartments of NW developed, C(L) decreased. At fast frequencies, a single compartment was found as the tidal volume of the slow compartment became smaller than its dead space; C(L) fell to 50% of its static value. Pendelluft and common dead space had only minimal effects on N_{2} clearance delay in the model. In 5 dogs with graded obstruction in a main bronchus and in 5 with large beads in lobar bronchi, increasing respiratory rate by transvenous phrenic nerve stimulation produced both fall in C(L) and increased N_{2} clearance delay. In 9 of 10 asymptomatic young smokers, NW at 6 frequencies from 10 to 110 breaths per minute revealed two compartments at one or more frequencies whereas in 10 non smokers the NW was a single exponential at all frequencies. Although NW in smokers did not completely follow the prediction from the model, frequency dependence of NW still appears to be a good non invasive method to detect small differences in time constants within the lung.

Original language | English |
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Journal | Federation Proceedings |

Volume | 32 |

Issue number | 3 |

State | Published - Dec 1 1973 |

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### ASJC Scopus subject areas

- Medicine(all)

### Cite this

*Federation Proceedings*,

*32*(3).