title: Lung diffusing capacity for nitric oxide at lowered and raised ambient pressures.
abstract: Lung diffusing capacity for NO (DLNO) was determined in eight subjects at ambient pressures of 505, 1015, and 4053hPa (379, 761 and 3040mmHg) as they breathed normoxic gases. Mean values were 116.9±11.1 (SEM), 113.4±11.1 and 99.3±10.1mlmin(-1)hPa(-1)at 505, 1015, and 4053hPa, with a 13% difference between the two higher pressures (P=0.017). The data were applied to a model with two serially coupled conductances; the gas phase (DgNO, variable with pressure), and the alveolo-capillary membrane (DmNO, constant). The data fitted the model well and we conclude that diffusive transport of NO in the peripheral lung is inversely related to gas density. At normal pressure DmNO was approximately 5% larger than DLNO, suggesting that the Dg factor then is not negligible. We also conclude that the density of the breathing gas is likely to impact the backdiffusion of naturally formed NO from conducting airways to the alveoli.
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet, SE-17177 Stockholm, Sweden. Electronic address: dag.linnarsson@ki.se.
authors.forename: Dag
authors.initials: D
authors.lastname: Linnarsson
authors.forename: Tryggve E
authors.initials: TE
authors.lastname: Hemmingsson
authors.forename: Claes
authors.initials: C
authors.lastname: Frostell
authors.forename: Alain
authors.initials: A
authors.lastname: Van Muylem
authors.forename: Yannick
authors.initials: Y
authors.lastname: Kerckx
authors.forename: Lars E
authors.initials: LE
authors.lastname: Gustafsson
mesh_terms: D000328:Adult; D001274:Atmospheric Pressure; D002199:Capillary Permeability; D005260:Female; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000502:physiology*; D011653:Pulmonary Diffusing Capacity / Q000502:physiology*; D055815:Young Adult
chemical_list: D009569:Nitric Oxide
keywords: Diffusivity; Gas density; Hyperbaria; Hypobaria; NO