title: The mechanism of deep inspiration-induced bronchoprotection: evidence from a mouse model.
abstract: In healthy individuals, deep inspirations (DIs) taken prior to a bronchial challenge reduce the bronchoconstrictor response, which is termed "bronchoprotection". The mechanism(s) of DI-induced bronchoprotection is unclear. The forced oscillation technique was used to assess the effect of prior DI on subsequent bronchoconstriction to methacholine (MCh) in BALB/c mice. We assessed likely mechanisms for the bronchoprotective effects of DI including reduced airway narrowing (from changes in airway resistance) and/or closure (changes in tissue elastance) and enhanced bronchodilation to a subsequent DI (% reversal in airway narrowing). DI prior to MCh challenge: 1) did not reduce but instead enhanced airway narrowing (p<0.05); 2) increased ventilation heterogeneity (p<0.05); 3) enhanced the subsequent bronchodilatory response to DI (p<0.05); and 4) reduced tissue elastance (p<0.05), suggesting opening of closed airways or alveoli units. Our findings suggest that DI prior to MCh challenge may elicit a series of changes, some of which are beneficial to respiratory function (enhanced bronchodilation), while others place greater load on the system (enhanced bronchoconstriction and ventilation heterogeneity). It is proposed that the relative magnitudes of these opposing physiological and mechanical effects will determine the net effect on respiratory function in health and disease.
authors.affiliation: Division of Clinical Sciences, Telethon Institute for Child Health Research, Subiaco, Italy.
authors.forename: Russell S
authors.initials: RS
authors.lastname: Wong
authors.forename: Alexander N
authors.initials: AN
authors.lastname: Larcombe
authors.forename: Lynette B
authors.initials: LB
authors.lastname: Fernandes
authors.forename: Graeme R
authors.initials: GR
authors.lastname: Zosky
authors.forename: Peter B
authors.initials: PB
authors.lastname: Noble
mesh_terms: D000403:Airway Resistance / Q000502:physiology*; D000818:Animals; D016535:Bronchial Hyperreactivity / Q000175:diagnosis; D001985:Bronchial Provocation Tests; D016084:Bronchoconstriction / Q000502:physiology*; D016085:Bronchoconstrictor Agents; D005260:Female; D001239:Inhalation / Q000502:physiology*; D016210:Methacholine Chloride; D051379:Mice; D008807:Mice, Inbred BALB C; D015656:Respiratory Mechanics / Q000502:physiology*
chemical_list: D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride