title: Gas exchange in the airways.
abstract: The primary function of the lungs is to exchange the respiratory gases, O2 and CO2, between the atmosphere and the blood. Our overall understanding of the lungs as a gas-exchanging organ has improved considerably over the past four decades. We now know that the dynamics of gas exchange depend on the blood solubility (beta b, ml gas ml blood-1 atm-1) of the gas. While the major focus of research has rightly been on the respiratory gases, the lungs exchange a wide spectrum of gases ranging from very low solubility gases such as SF6 or helium (beta b = 0.01) to water vapor (beta b = 20,000). O2 (beta b = 0.7) and CO2 (beta b = 3.0) exchange primarily in the alveolar region of the lung and their exchange is limited by the rate of ventilation and perfusion. In contrast, highly soluble gases (beta b > 100) are likely to exchange primarily in the airways of the lung. We have used exhaled ethanol (beta b = 1756) profiles for humans, steady-state exchange of six inert gases (0.01 < beta b < 300) in an in situ dog trachea, and a mathematical model to analyze the dynamics of airway gas exchange. We make the following conclusion: (1) ethanol exchanges entirely within the airways, and (2) the magnitude of perfusion- and diffusion-related resistance to airway gas exchange is the same.
authors.affiliation: Department of Chemical Engineering, University of Washington, Seattle 98195, USA.
authors.forename: S C
authors.initials: SC
authors.lastname: George
authors.forename: M P
authors.initials: MP
authors.lastname: Hlastala
authors.forename: J E
authors.initials: JE
authors.lastname: Souders
authors.forename: A L
authors.initials: AL
authors.lastname: Babb
mesh_terms: D000818:Animals; D015824:Blood-Air Barrier / Q000502:physiology*; D001944:Breath Tests; D004285:Dogs; D000431:Ethanol / Q000493:pharmacokinetics; D006801:Humans; D008297:Male; D008954:Models, Biological; D008962:Models, Theoretical; D005741:Noble Gases / Q000493:pharmacokinetics; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D014132:Trachea / Q000378:metabolism*