title: Deep inspiration volume and the impaired reversal of bronchoconstriction in asthma.
abstract: It is unclear whether the failure to reverse bronchoconstriction with deep inspiration (DI) in asthma is due to reduced maximal dilatation of the DI. We compared the effect of different DI volumes on maximal dilatation and reversal of bronchoconstriction in nine asthmatics and ten non-asthmatics. During bronchoconstriction, subjects took DI to 40%, 70% and 100% inspiratory capacity, on separate days. Maximal dilatation was measured as respiratory system resistance (Rrs) at end-inspiration and residual dilatation as Rrs at end-expiration, both expressed as percent of Rrs at end-tidal expiration prior to DI. DI volume was positively associated with maximal dilatation in non-asthmatics (ANOVA p=0.055) and asthmatics (p=0.023). DI volume was positively associated with residual dilatation in non-asthmatics (p=0.004) but not in asthmatics (p=0.53). The degree of maximal dilatation independently predicted residual dilatation in non-asthmatics but not asthmatics. These findings suggest that the failure to reverse bronchoconstriction with DI in asthma is not due to reduced maximal dilatation, but rather due to increased airway narrowing during expiration.
authors.affiliation: Medical School, University of Sydney, NSW 2006, Australia.
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Hulme
authors.forename: Cheryl M
authors.initials: CM
authors.lastname: Salome
authors.forename: Nathan J
authors.initials: NJ
authors.lastname: Brown
authors.forename: Norbert
authors.initials: N
authors.lastname: Berend
authors.forename: Helen M
authors.initials: HM
authors.lastname: Agus
authors.forename: Karla R
authors.initials: KR
authors.lastname: Horlyck
authors.forename: Greg G
authors.initials: GG
authors.lastname: King
authors.forename: David G
authors.initials: DG
authors.lastname: Chapman
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001249:Asthma / Q000188:drug therapy* / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D016084:Bronchoconstriction / Q000187:drug effects* / Q000502:physiology*; D005260:Female; D005541:Forced Expiratory Volume / Q000187:drug effects; D006801:Humans; D007320:Inspiratory Capacity / Q000187:drug effects; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology / Q000627:therapeutic use*; D018721:Muscarinic Agonists / Q000494:pharmacology / Q000627:therapeutic use*; D055815:Young Adult
chemical_list: D018721:Muscarinic Agonists; D016210:Methacholine Chloride
keywords: Airway hyperresponsiveness; Airway physiology; Asthma; Deep inspiration