title: Exhaled Particles After a Standardized Breathing Maneuver.
abstract: BACKGROUND
  Particles in exhaled air (PEx) provide samples of respiratory tract lining fluid from small airways and offer a new opportunity to monitor pathological changes. The exhaled particles are produced by reopening of closed small airways and contain surfactant. The amount of PEx varies by orders of magnitude among subjects. A standardized breathing pattern reduces the variation, but it remains large and the reasons are unknown. The aim of the present study was to assess to what extent sex, age, body size, and spirometry results explain the interindividual variation of PEx among healthy middle-aged subjects.
  
  
  METHODS
  The PExA®instrument was used to measure PEx in 126 healthy middle-aged nonsmoking subjects participating in the European Respiratory Community Health Survey (ERCS-III). The subjects performed a standardized breathing maneuver involving expiration to residual volume, a breath-hold of 3 seconds, a full inspiration, and then a full expiration into the PExA instrument. PEx number concentrations were expressed per exhalation and per exhaled liter. Age and anthropometric and spirometric variables were analyzed as potential predictors.
  
  
  RESULTS
  PEx/L was consistently and negatively associated to lung size-related variables and accordingly lower in men than in women. PEx/Exhalation was similar in women and men. Increasing age was associated with increasing PEx. Reference equations are presented based on age, weight, and spirometry variables and independent of sex. These predictors explained 28%-29% of the interindividual variation.
  
  
  CONCLUSIONS
  The interindividual variation of PEx after a standardized breathing maneuver is large and the considered predictors explain a minor part only.
authors.affiliation: 1 Department of Respiratory Medicine and Allergology, Sahlgrenska Academy at University of Gothenburg , Gothenburg, Sweden .
authors.forename: Björn
authors.initials: B
authors.lastname: Bake
authors.affiliation: 2 Department of Chemistry and Molecular Biology, University of Gothenburg , Gothenburg, Sweden .
authors.forename: Evert
authors.initials: E
authors.lastname: Ljungström
authors.affiliation: 3 Department of Occupational and Environmental Medicine, Sahlgrenska Academy at University of Gothenburg , Gothenburg, Sweden .
authors.forename: Annika
authors.initials: A
authors.lastname: Claesson
authors.affiliation: 3 Department of Occupational and Environmental Medicine, Sahlgrenska Academy at University of Gothenburg , Gothenburg, Sweden .
authors.forename: Hanne Krage
authors.initials: HK
authors.lastname: Carlsen
authors.affiliation: 3 Department of Occupational and Environmental Medicine, Sahlgrenska Academy at University of Gothenburg , Gothenburg, Sweden .
authors.forename: Matthias
authors.initials: M
authors.lastname: Holm
authors.affiliation: 3 Department of Occupational and Environmental Medicine, Sahlgrenska Academy at University of Gothenburg , Gothenburg, Sweden .
authors.forename: Anna-Carin
authors.initials: AC
authors.lastname: Olin
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000367:Age Factors; D000368:Aged; D045853:Exhalation / Q000502:physiology*; D005260:Female; D006801:Humans; D008168:Lung / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011663:Pulmonary Surfactants / Q000378:metabolism; D012015:Reference Standards; D012119:Respiration; D012137:Respiratory System / Q000378:metabolism; D012737:Sex Factors; D013147:Spirometry / Q000379:methods*
chemical_list: D011663:Pulmonary Surfactants
keywords: BMI; aerosol distribution; age; airway closure; airway opening; breathing maneuver; healthy subjects; height; lung function; physiology; respiratory tract lining fluid; sex; ventilation; weight