title: A first principles calculation of the oxygen uptake in the human pulmonary acinus at maximal exercise.
abstract: It has recently been shown that the acinus can have a reduced efficiency due to a "screening effect" governed by the ratio of oxygen diffusivity to membrane permeability, the gas flow velocity, as well as the size and configuration of the acinus. We present here a top to bottom calculation of the functioning of a machine acinus at exercise that takes this screening effect into account. It shows that, given the geometry and the breathing dynamics of real acini, respiration can be correlated to a single equivalent parameter that we call the integrative permeability. In particular we find that both V(O(2,max)) and PA(O(2)) depend on this permeability in a non-linear manner. Numerical solutions of dynamic convection-diffusion equations indicate that only a narrow range of permeability values is compatible with the experimental measurements of PA(O(2)) and V(O(2,max)). These permeability values are significantly smaller than those found in the literature. In a second step, we present a new type of evaluation of the diffusive permeability, yielding values compatible with the top to bottom approach, but smaller than the usual morphometric value.
authors.affiliation: Physique de la Matière Condensée, CNRS, Ecole Polytechnique, 91128 Palaiseau, France.
authors.forename: A
authors.initials: A
authors.lastname: Foucquier
authors.forename: M
authors.initials: M
authors.lastname: Filoche
authors.forename: A A
authors.initials: AA
authors.lastname: Moreira
authors.forename: J S
authors.initials: JS
authors.lastname: Andrade
authors.forename: G
authors.initials: G
authors.lastname: Arbia
authors.forename: B
authors.initials: B
authors.lastname: Sapoval
mesh_terms: D061354:Acinar Cells / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D011650:Pulmonary Alveoli / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology*
chemical_list: D010100:Oxygen