title: Effect of airway opening on production of exhaled particles.
abstract: The technique of sampling exhaled air is attractive because it is noninvasive and so allows repeated sampling with ease and no risk for the patient. Knowledge of the biomarkers' origin is important to correctly understand and interpret the data. Endogenous particles, formed in the airways, are exhaled and reflect chemical composition of the respiratory tract lining fluid. However, the formation mechanisms and formation sites of these particles are unknown. We hypothesize that airway opening following airway closure causes production of airborne particles that are exhaled. The objective of this study was to examine production of exhaled particles following varying degrees of airway closure. Ten healthy volunteers performed three different breathing maneuvers in which the initial lung volume preceding an inspiration to total lung capacity was varied between functional residual capacity (FRC) and residual volume (RV). Exhaled particle number concentrations in the size interval 0.30-2.0 microm were recorded. Number concentrations of exhaled particles showed a 2- to 18-fold increase after exhalations to RV compared with exhalations where no airway closure was shown [8,500 (810-28,000) vs. 1,300 (330-13,000) particles/expired liter, P = 0.012]. The difference was most noticeable for the smaller size range of particles (<1 microm). There were significant correlations between particle concentrations for the different maneuvers. Our results show that airway reopening following airway closure is an important mechanism for formation of endogenous exhaled particles and that these particles originate from the terminal bronchioles.
authors.affiliation: Occupational and Environmental Medicine at Sahlgrenska Academy, Box 414, SE-405 30 Gothenburg, Sweden. ann-charlotte.almstrand@amm.gu.se
authors.forename: Ann-Charlotte
authors.initials: AC
authors.lastname: Almstrand
authors.forename: Björn
authors.initials: B
authors.lastname: Bake
authors.forename: Evert
authors.initials: E
authors.lastname: Ljungström
authors.forename: Per
authors.initials: P
authors.lastname: Larsson
authors.forename: Anna
authors.initials: A
authors.lastname: Bredberg
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Mirgorodskaya
authors.forename: Anna-Carin
authors.initials: AC
authors.lastname: Olin
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000378:metabolism*; D001944:Breath Tests / Q000295:instrumentation; D055745:Bronchioles / Q000378:metabolism; D004867:Equipment Design; D045853:Exhalation; D005260:Female; D005652:Functional Residual Capacity; D006801:Humans; D001239:Inhalation; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D010316:Particle Size; D012115:Residual Volume; D012137:Respiratory System / Q000378:metabolism*; D013147:Spirometry; D014109:Total Lung Capacity
chemical_list: D015415:Biomarkers