title: The effect of posture-induced changes in peripheral nitric oxide uptake on exhaled nitric oxide.
abstract: Airway and alveolar NO contributions to exhaled NO are being extracted from exhaled NO measurements performed at different flow rates. To test the robustness of this method and the validity of the underlying model, we deliberately induced a change in NO uptake in the peripheral lung compartment by changing body posture between supine and prone. In 10 normal subjects, we measured exhaled NO at target flows ranging from 50 to 350 ml/s in supine and prone postures. Using two common methods, bronchial NO production [Jaw(NO)] and alveolar NO concentration (FANO) were extracted from exhaled NO concentration vs. flow or flow(-1) curves. There was no significant Jaw(NO) difference between prone and supine but a significant FANO decrease from prone to supine ranging from 23 to 33% depending on the method used. Total lung capacity was 7% smaller supine than prone (P = 0.03). Besides this purely volumetric effect, which would tend to increase FANO from prone to supine, the observed degree of FANO decrease from prone to supine suggests a greater opposing effect that could be explained by the increased lung capillary blood volume (V(c)) supine vs. prone (P = 0.002) observed in another set of 11 normal subjects. Taken together with the relative changes of NO and CO transfer factors, this V(c) change can be attributed mainly to pulmonary capillary recruitment from prone to supine. Realistic models for exhaled NO simulation should include the possibility that a portion of the pulmonary capillary bed is unavailable for NO uptake, with a maximum capacity of the pulmonary capillary bed in the supine posture.
authors.affiliation: Respiratory Division, Univ. Hospital UZ Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium. sylvia.verbanck@uzbrussel.be
authors.forename: Sylvia
authors.initials: S
authors.lastname: Verbanck
authors.forename: Yannick
authors.initials: Y
authors.lastname: Kerckx
authors.forename: Daniel
authors.initials: D
authors.lastname: Schuermans
authors.forename: Claire
authors.initials: C
authors.lastname: de Bisschop
authors.forename: Hervé
authors.initials: H
authors.lastname: Guénard
authors.forename: Robert
authors.initials: R
authors.lastname: Naeije
authors.forename: Walter
authors.initials: W
authors.lastname: Vincken
authors.forename: Alain
authors.initials: A
authors.lastname: Van Muylem
mesh_terms: D000328:Adult; D001944:Breath Tests / Q000379:methods; D001993:Bronchodilator Agents / Q000378:metabolism*; D045853:Exhalation / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D016684:Prone Position / Q000502:physiology*; D011650:Pulmonary Alveoli / Q000502:physiology; D011653:Pulmonary Diffusing Capacity; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D016683:Supine Position / Q000502:physiology*
chemical_list: D001993:Bronchodilator Agents; D009569:Nitric Oxide