title: Lung clearance index in adults with non-cystic fibrosis bronchiectasis.
abstract: BACKGROUND
  Lung clearance index (LCI) is a measure of abnormal ventilation distribution derived from the multiple breath inert gas washout (MBW) technique. We aimed to determine the clinical utility of LCI in non-CF bronchiectasis, and to assess two novel MBW parameters that distinguish between increases in LCI due to specific ventilation inequality (LCIvent) and increased respiratory dead space (LCIds).
  
  
  METHODS
  Forty-three patients with non-CF bronchiectasis and 18 healthy control subjects underwent MBW using the sulphur hexafluoride wash-in technique, and data from 40 adults with CF were re-analysed. LCIvent and LCIds were calculated using a theoretical two-compartment lung model, and represent the proportional increase in LCI above its ideal value due to specific ventilation inequality and increased respiratory dead space, respectively.
  
  
  RESULTS
  LCI was significantly raised in patients with non-CF bronchiectasis compared to healthy controls (9.99 versus 7.28, p < 0.01), and discriminated well between these two groups (area under receiver operating curve = 0.90, versus 0.83 for forced expiratory volume in one second [% predicted]). LCI, LCIvent and LCIds were repeatable (intraclass correlation coefficient > 0.75), and correlated significantly with measures of spirometric airflow obstruction.
  
  
  CONCLUSIONS
  LCI is repeatable, discriminatory, and is associated with spirometric airflow obstruction in patients with non-CF bronchiectasis. LCIvent and LCIds are a practical and repeatable alternative to phase III slope analysis and may allow a further level of mechanistic information to be extracted from the MBW test in patients with severe ventilation heterogeneity.
authors.affiliation: Institute for Lung Health, University of Leicester, Leicester, UK. sg330@le.ac.uk.
authors.forename: Sherif
authors.initials: S
authors.lastname: Gonem
authors.forename: Alys
authors.initials: A
authors.lastname: Scadding
authors.forename: Marcia
authors.initials: M
authors.lastname: Soares
authors.forename: Amisha
authors.initials: A
authors.lastname: Singapuri
authors.forename: Per
authors.initials: P
authors.lastname: Gustafsson
authors.forename: Chandra
authors.initials: C
authors.lastname: Ohri
authors.forename: Simon
authors.initials: S
authors.lastname: Range
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Brightling
authors.forename: Ian
authors.initials: I
authors.lastname: Pavord
authors.forename: Alex
authors.initials: A
authors.lastname: Horsley
authors.forename: Salman
authors.initials: S
authors.lastname: Siddiqui
mesh_terms: D000328:Adult; D000368:Aged; D001987:Bronchiectasis / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D003550:Cystic Fibrosis; D005260:Female; D006801:Humans; D008168:Lung / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009079:Mucociliary Clearance / Q000502:physiology*; D012123:Pulmonary Ventilation / Q000502:physiology*; D055815:Young Adult