Diffusional screening in the human pulmonary acinus

• Published in: Journal of applied physiology (1985) 2003-05, Vol.94 (5), p.2010-2016
• Main Authors: Felici, M, Filoche, M, Sapoval, B
• Format: Article
• Language: English
• Subjects: Air breathing; Algorithms; Biological and medical sciences; Cell Membrane Permeability; Diffusion; Fundamental and applied biological sciences. Psychology; Humans; Lungs; Mathematical models; Models, Biological; Models, Statistical; Oxygen; Oxygen Consumption - physiology; Pulmonary Alveoli - physiology; Respiratory system; Respiratory system: anatomy, metabolism, gas exchange, ventilatory mechanics, respiratory hemodynamics; Vertebrates: respiratory system
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00913.2002

1  Laboratoire de Physique de la Matière Condensée, Centre National de la Recherche Scientifique, Ecole Polytechnique, 91128 Palaiseau; and 2  Centre de Mathématiques et leurs Applications, Centre National de la Recherche Scientifique, Ecole Normale Supérieure de Cachan, 94235 Cachan, France In the mammalian lung acini, O 2 diffuses into quasi-static air toward the alveolar membrane, where the gas exchange with blood takes place. The O 2 flux is then influenced by the O 2 diffusivity, the membrane permeability, and the acinus geometric complexity. This phenomenon has been recently studied in an abstract geometric model of the acinus, the Hilbert acinus (Sapoval B, Filoche M, and Weibel ER, Proc Natl Acad Sci USA 99: 10411, 2002). This is extended here to a more realistic geometry originated from the morphological model of Kitaoka et al. (Kitaoka K, Tamura S, and Takaki R, J Appl Physiol 88: 2260-2268, 2000). Two-dimensional numerical simulations of the steady-state diffusion equation with mixed boundary conditions are used to quantify the process. The alveolar O 2 concentration, or partial pressure, and the O 2 flux are computed and show that diffusional screening exists at rest. These results confirm that smaller acini are more efficient, as suggested for the Hilbert acini. oxygen diffusion; acinar gas mixing; mathematical modeling