• Diffusion of gases into the lung: How physics can help to understand physiology

• Fulltext

https://www.ias.ac.in/article/fulltext/pram/071/02/0245-0251

• Keywords

Lung; diffusion; screening; efficiency; edema.

• Abstract

In the human lung, the gas transfer between air and blood is achieved in terminal units that are called acini'. Whereas convection is still the predominant transport phenomenon at the acinus entrance, most of the acinar surface is in fact accessed by diffusion. The transition between convection and diffusion, and thus the size of the diffusion unit, depends on the air velocity at the acinus entrance. In this paper, we present a gas transport model which takes into account both the diffusion into the acinus and the diffusion across the alveolar membrane. It is shown that the physiological sizes of the diffusion unit in the lung, at rest or at exercise, can be explained by physical arguments. In that sense, diffusion is the dimensioning criterion' of the lung at the acinar level. This approach shows that, due to diffusional screening at inspiration and at rest, there exists a permanent spatial inhomogeneity of oxygen and carbon dioxide partial pressure which reduces the effective surface efficiency of the human acinus to a value of only 30 to 40%. This model casts a new light on the properties of this physiological transport system. It permits in particular to understand how several diseases among which pulmonary edema may remain asymptomatic in their early stages.

• Author Affiliations

1. Physique de la Matière Condensée, Ecole Polytechnique, CNRS, 91128 Palaiseau, France
2. CMLA, ENS Cachan, CNRS, UniverSud, 61 Avenue du President Wilson, F-94230 Cachan, France

• Pramana – Journal of Physics

Volume 94, 2020
All articles
Continuous Article Publishing mode

• Editorial Note on Continuous Article Publication

Posted on July 25, 2019