title: Single-Breath Washout Tests to Assess Small Airway Disease in COPD.
abstract: BACKGROUND
  Current functional assessments do not allow a reliable assessment of small airways, which are a major site of disease in COPD. Single-breath washout (SBW) tests are feasible and reproducible methods for evaluating small airway disease. Their relevance in COPD remains unknown.
  
  
  METHODS
  We performed a cross-sectional study in 65 patients with moderate to severe COPD. Phase III slope of nitrogen (SIIIN2) and double tracer gas (SIIIDTG) SBW tests were used as a measure of ventilation inhomogeneity. The association of both markers with established physiological and clinical features of COPD was assessed.
  
  
  RESULTS
  Ventilation inhomogeneity as measured by SIIIN2and SIIIDTGwas increased in patients with COPD compared with healthy subjects (P < .001 and P < .001, respectively). SIIIN2was associated with FEV1predicted, residual volume (RV)/total lung capacity (TLC) and diffusing capacity of the lung for carbon monoxide (Dlco) (all P < .001). Furthermore, SIIIN2was related to dyspnea, exercise-induced desaturation, and exercise capacity (P = .001, P < .001, and P = .047, respectively). SIIIDTGwas associated with TLC, Dlco, and cough (P < .001, P = .001, and P = .009, respectively). In multivariate regression models, we demonstrated that these associations are largely independent of FEV1and mostly stronger than associations with FEV1. In contrast, FEV1was superior in predicting emphysema severity.
  
  
  CONCLUSIONS
  SIIIN2and SIIIDTG, two fast and clinically applicable measures of small airway disease, reflect different physiological and clinical aspects of COPD, largely independent of spirometry.
  
  
  BACKGROUND
  ISRCTN99586989, Ethics committee Beider Basel (approval number 295/07).
authors.affiliation: Clinic of Respiratory Medicine and Pulmonary Cell Research, University Hospital Basel, Switzerland.
authors.forename: Lucas
authors.initials: L
authors.lastname: Boeck
authors.affiliation: Division of Respiratory Medicine, University Children's Hospital Basel, Switzerland.
authors.forename: Anna
authors.initials: A
authors.lastname: Gensmer
authors.affiliation: Division of Respiratory Medicine, University Children's Hospital Basel, Switzerland; Pediatric Respiratory Medicine, University Children's Hospital Bern, University of Bern, Switzerland.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Nyilas
authors.affiliation: Clinic of Radiology and Nuclear Medicine, University Hospital Basel, Switzerland.
authors.forename: Bram
authors.initials: B
authors.lastname: Stieltjes
authors.affiliation: Clinic of Radiology and Nuclear Medicine, University Hospital Basel, Switzerland.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Re
authors.affiliation: Clinic of Respiratory Medicine and Pulmonary Cell Research, University Hospital Basel, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Tamm
authors.affiliation: Division of Respiratory Medicine, University Children's Hospital Basel, Switzerland; Pediatric Respiratory Medicine, University Children's Hospital Bern, University of Bern, Switzerland.
authors.forename: Philipp
authors.initials: P
authors.lastname: Latzin
authors.affiliation: Clinic of Respiratory Medicine and Pulmonary Cell Research, University Hospital Basel, Switzerland. Electronic address: daiana.stolz@usb.ch.
authors.forename: Daiana
authors.initials: D
authors.lastname: Stolz
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D015203:Reproducibility of Results; D012129:Respiratory Function Tests
keywords: COPD; lung function; physiology; small airway disease