### Abstract

Data from eighteen subjects, studied in hypoxia (minimum PI_{O2} = 80 Torr) both at rest and during exercise, were analyzed using computer models which estimate O_{2} diffusing capacity from measured V̇A/Q̇ distributions (obtained using the multiple inert gas elimination technique 'MIGET') and measured O_{2} exchange. Two of these models assigned the distribution of the diffusing capacity (D) in proportion to either the perfusion (DL_{O2}-Vwt) distributions from MIGET, and thus modeled the effects of V̇A/Q̇ and D/Q̇β(where Q̇β is the perfusive conductance inequalities respectively. The third model (DL_{O2}-3C) assigned all the diffusing capacity to a single homogeneous compartment. At rest DL_{O2} was 41.1 ± 41.4 ± 5.4 and 30.2 ± 2.1 ml · min^{-1} · Torr^{-1} for the Qwt, Vwt and 3C models respectively. These rose to 93.7 ± 2.6, 109.3 ± 4.5 and 81.1 ± 1.9 ml · min^{-1} · Torr^{-1} respectively at maximal exercise, all significantly different from rest (P < 0.001 for each). The effects of measured V̇A/Q̇ and theoretical D/Q̇β inhomogeneities on diffusing capacity estimates were significant even in normal lungs. Both types of inequality caused an appreciable underestimation of DL_{O2}. These multi-compartment model estimates, using real data, are consistent with published theoretical predictions of the effects of V̇, Q̇ and D inequalities. These results during exercise come close to morphometric predictions of maximal oxygen diffusing capacity in man.

Original language | English (US) |
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Pages (from-to) | 129-147 |

Number of pages | 19 |

Journal | Respiration Physiology |

Volume | 69 |

Issue number | 2 |

DOIs | |

State | Published - 1987 |

Externally published | Yes |

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### Keywords

- Exercise
- Hypoxia
- Inert gases
- Lung models
- Pulmonary gas exchange

### ASJC Scopus subject areas

- Physiology
- Pulmonary and Respiratory Medicine

### Cite this

*Respiration Physiology*,

*69*(2), 129-147. https://doi.org/10.1016/0034-5687(87)90022-3