title: Exhaled breath condensate pH is a robust and reproducible assay of airway acidity.
abstract: Exhaled breath condensate (EBC) pH is low in several lung diseases and it normalises with therapy. The current study examined factors relevant to EBC pH monitoring. Intraday and intraweek variability were studied in 76 subjects. The pH of EBC collected orally and from isolated lower airways was compared in an additional 32 subjects. Effects of ventilatory pattern (hyperventilation/hypoventilation), airway obstruction after methacholine, temperature (-44 to +13 degrees C) and duration of collection (2-7 min), and duration of sample storage (up to 2 yrs) were examined. All samples were collected with a disposable condensing device, and de-aerated with argon until pH measurement stabilised. Mean EBC pH (n=76 subjects, total samples=741) was 7.7+/-0.49 (mean+/-SD). Mean intraweek and intraday coefficients of variation were 4.5% and 3.5%. Control of EBC pH appears to be at the level of the lower airway. Temperature of collection, duration of collection and storage, acute airway obstruction, subject age, saliva pH, and profound hyperventilation and hypoventilation had no effect on EBC pH. The current authors conclude that in health, exhaled breath condensate pH is slightly alkaline, held in a narrow range, and is controlled by lower airway source fluid. Measurement of exhaled breath condensate pH is a simple, robust, reproducible and relevant marker of disease.
authors.affiliation: Division of Pediatric Respiratory Medicine, University of Virginia, Charlottesville, Virginia 22908, USA.
authors.forename: J
authors.initials: J
authors.lastname: Vaughan
authors.forename: L
authors.initials: L
authors.lastname: Ngamtrakulpanit
authors.forename: T N
authors.initials: TN
authors.lastname: Pajewski
authors.forename: R
authors.initials: R
authors.lastname: Turner
authors.forename: T A
authors.initials: TA
authors.lastname: Nguyen
authors.forename: A
authors.initials: A
authors.lastname: Smith
authors.forename: P
authors.initials: P
authors.lastname: Urban
authors.forename: S
authors.initials: S
authors.lastname: Hom
authors.forename: B
authors.initials: B
authors.lastname: Gaston
authors.forename: J
authors.initials: J
authors.lastname: Hunt
mesh_terms: D000136:Acid-Base Equilibrium / Q000502:physiology; D000293:Adolescent; D000328:Adult; D015415:Biomarkers; D001944:Breath Tests / Q000379:methods*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008171:Lung Diseases / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012137:Respiratory System / Q000503:physiopathology*
chemical_list: D015415:Biomarkers