title: Effects of cystic fibrosis lung disease on gas mixing indices derived from alveolar slope analysis.
abstract: S(cond) and S(acin) are derived from analysis of concentration-normalized phase III slopes (Sn(III)) of a multiple breath inert gas washout. Studies in healthy and COPD subjects suggest these reflect ventilation heterogeneity in conducting and acinar airway zones respectively, but similar studies in cystic fibrosis (CF) are lacking. S(cond), S(acin) and lung clearance index (LCI, a measure of overall gas mixing efficiency) were measured in 22 adults and 18 children with CF and 17 adult and 29 child controls. Plethysmography and gas transfer measurements were performed in adults, and spirometry in all subjects. S(cond) was elevated in almost all CF patients, including children with mild disease and normal LCI. However, S(cond) did not correlate with other measurements and appeared to reach a maximum; further increase in ventilation heterogeneity being restricted to S(acin). The nature and/or severity of CF lung disease may invalidate assumptions underlying the ability to separate phase III slope analysis of ventilation heterogeneity into proximal and peripheral components, and LCI may be a better indicator of gas mixing in this population.
authors.affiliation: University of Edinburgh and Department of Respiratory Medicine, Western General Hospital, Edinburgh EH4 2XU, UK. alex.horsley@ed.ac.uk
authors.forename: Alex R
authors.initials: AR
authors.lastname: Horsley
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Macleod
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Robson
authors.forename: Jill
authors.initials: J
authors.lastname: Lenney
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Bell
authors.forename: Steve
authors.initials: S
authors.lastname: Cunningham
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Greening
authors.forename: Per M
authors.initials: PM
authors.lastname: Gustafsson
authors.forename: J Alastair
authors.initials: JA
authors.lastname: Innes
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D003550:Cystic Fibrosis / Q000175:diagnosis* / Q000503:physiopathology*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010991:Plethysmography; D012123:Pulmonary Ventilation / Q000187:drug effects / Q000502:physiology*; D012119:Respiration / Q000187:drug effects*; D012129:Respiratory Function Tests / Q000379:methods*; D055815:Young Adult