title: Sampling airway surface liquid: non-volatiles in the exhaled breath condensate.
abstract: Exhaled breath condensate (EBC) samples contain molecules that have no appreciable vapor pressure; such molecules likely derive from droplets of airway fluid. We analyzed EBC gathered from a total of 62 healthy volunteers in order to quantify the volume of airway liquid that was the source of the non-volatiles; saliva was analyzed as a reference secretion. EBC urea averaged 0.52 +/- 0.12 micromol/L (n = 18), an 8,600-fold dilution from predicted blood urea nitrogen levels. Protein averaged 2.3 +/- 0.3 microg/ml (n = 31), three orders of magnitude less than in saliva (1.4 +/- 0.1 mg/ml, n = 15). EBC ammonia was 6.6 +/- 0.6 mmol/L (1/15 that of saliva) and EBC ammonium ion was 0.90 +/- 0.19 micromol/L, concentrations that are incompatible with an 8,600-fold dilution from a biological source. Thus, urea-derived dilution factors may be used to interpret EBC non-volatile molecules, but not EBC volatiles.
authors.affiliation: Department of Physiology and Biophysics, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 30216-4505, USA. tdwyer@physiology.umsmed.edu
authors.forename: Terry M
authors.initials: TM
authors.lastname: Dwyer
mesh_terms: D000418:Albumins / Q000378:metabolism; D000641:Ammonia / Q000378:metabolism; D001944:Breath Tests / Q000379:methods*; D045853:Exhalation / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D011506:Proteins / Q000378:metabolism; D012016:Reference Values; D012129:Respiratory Function Tests; D013048:Specimen Handling / Q000379:methods; D013499:Surface Properties; D014508:Urea / Q000378:metabolism*
chemical_list: D000418:Albumins; D011506:Proteins; D000641:Ammonia; D014508:Urea