### Abstract

Piiper and Scheid (Resp. Physiol. 23: 209-221, 1975) compared different models of external gas exchange with performance indices defined as functions of ventilatory/perfusive and diffusive/perfusive conductance ratios (Gvent/Gperf and Gdiff/Gperf, where Gdiff is diffusing capacity). We expanded their analysis to include: (1) Δp_{D}, the average partial pressure gradient driving diffusion across the exchange barrier, normalized to the maximum gradient available (Pi-Pv), and (2) Jdiff, the sensitivity of total conductance to changes in Gdiff, where total conductance is the ratio of gas flux to the maximum gradient [Gtot = M ̇/(Pi-Pv)]. Although the counter-current model is most efficient, it is more sensitive than cross-current or ventilated pool models to changes in Gdiff. For given Gvent, Gperf and Pi-Pv, maximum Gtot may not be achieved in the counter-current model until Gdiff is over ten-fold greater than that necessary for maximum Gtot in the other models. Experimental data also shows greater Jdiff and diffusion limitation in fish than in birds or mammals. We conclude that counter-current O_{2} exchange cannot approach ideal levels as closely as the ventilated pool or cross-current models in nature.

Original language | English (US) |
---|---|

Pages (from-to) | 17-29 |

Number of pages | 13 |

Journal | Respiration Physiology |

Volume | 91 |

Issue number | 1 |

DOIs | |

State | Published - 1993 |

Externally published | Yes |

### Fingerprint

### Keywords

- Alveolar gas exchange, models, diffusion limitation
- Cutaneous gas exchange
- Diffusion, limitation, vertebrate external gas exchange
- Models, external gas exchange, vertebrates
- Parabronchial gas exchange

### ASJC Scopus subject areas

- Physiology
- Pulmonary and Respiratory Medicine

### Cite this

*Respiration Physiology*,

*91*(1), 17-29. https://doi.org/10.1016/0034-5687(93)90086-P

**Diffusion limitation in comparative models of gas exchange.** / Powell, Frank L.; Hempleman, Steven C.

Research output: Contribution to journal › Article

*Respiration Physiology*, vol. 91, no. 1, pp. 17-29. https://doi.org/10.1016/0034-5687(93)90086-P

}

TY - JOUR

T1 - Diffusion limitation in comparative models of gas exchange

AU - Powell, Frank L.

AU - Hempleman, Steven C

PY - 1993

Y1 - 1993

N2 - Piiper and Scheid (Resp. Physiol. 23: 209-221, 1975) compared different models of external gas exchange with performance indices defined as functions of ventilatory/perfusive and diffusive/perfusive conductance ratios (Gvent/Gperf and Gdiff/Gperf, where Gdiff is diffusing capacity). We expanded their analysis to include: (1) ΔpD, the average partial pressure gradient driving diffusion across the exchange barrier, normalized to the maximum gradient available (Pi-Pv), and (2) Jdiff, the sensitivity of total conductance to changes in Gdiff, where total conductance is the ratio of gas flux to the maximum gradient [Gtot = M ̇/(Pi-Pv)]. Although the counter-current model is most efficient, it is more sensitive than cross-current or ventilated pool models to changes in Gdiff. For given Gvent, Gperf and Pi-Pv, maximum Gtot may not be achieved in the counter-current model until Gdiff is over ten-fold greater than that necessary for maximum Gtot in the other models. Experimental data also shows greater Jdiff and diffusion limitation in fish than in birds or mammals. We conclude that counter-current O2 exchange cannot approach ideal levels as closely as the ventilated pool or cross-current models in nature.

AB - Piiper and Scheid (Resp. Physiol. 23: 209-221, 1975) compared different models of external gas exchange with performance indices defined as functions of ventilatory/perfusive and diffusive/perfusive conductance ratios (Gvent/Gperf and Gdiff/Gperf, where Gdiff is diffusing capacity). We expanded their analysis to include: (1) ΔpD, the average partial pressure gradient driving diffusion across the exchange barrier, normalized to the maximum gradient available (Pi-Pv), and (2) Jdiff, the sensitivity of total conductance to changes in Gdiff, where total conductance is the ratio of gas flux to the maximum gradient [Gtot = M ̇/(Pi-Pv)]. Although the counter-current model is most efficient, it is more sensitive than cross-current or ventilated pool models to changes in Gdiff. For given Gvent, Gperf and Pi-Pv, maximum Gtot may not be achieved in the counter-current model until Gdiff is over ten-fold greater than that necessary for maximum Gtot in the other models. Experimental data also shows greater Jdiff and diffusion limitation in fish than in birds or mammals. We conclude that counter-current O2 exchange cannot approach ideal levels as closely as the ventilated pool or cross-current models in nature.

KW - Alveolar gas exchange, models, diffusion limitation

KW - Cutaneous gas exchange

KW - Diffusion, limitation, vertebrate external gas exchange

KW - Models, external gas exchange, vertebrates

KW - Parabronchial gas exchange

UR - http://www.scopus.com/inward/record.url?scp=0027391838&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0027391838&partnerID=8YFLogxK

U2 - 10.1016/0034-5687(93)90086-P

DO - 10.1016/0034-5687(93)90086-P

M3 - Article

VL - 91

SP - 17

EP - 29

JO - Respiratory Physiology and Neurobiology

JF - Respiratory Physiology and Neurobiology

SN - 1569-9048

IS - 1

ER -