title: Different respiratory behaviors disclosed by induced bronchoconstriction in mild asthma patients.
abstract: Respiratory responses to bronchoconstriction in asthma have been partially assessed and their significance is unclear. In 44 mild asthma patients we investigated respiratory responses during increasing levels of methacholine-induced bronchoconstriction. Inspiratory muscle activity, tidal volume, inspiratory and expiratory times were continuously monitored; breathing discomfort was rated. Mean inspiratory flow, respiratory frequency and ventilation were calculated. Lung function was assessed prior to and at maximum bronchoconstriction. Bronchoconstriction "dose-dependently" increased inspiratory muscle activity and breathing discomfort (P<0.01). In 37 patients (84.1%), the increase in inspiratory muscle activity was associated with increases in mean inspiratory flow and ventilation (P<0.01) because of selective rises in breathing depth (volume responders), or rate (frequency responders) or both (dual responders). In seven patients (15.9%) ventilation was unchanged. Individual respiratory responses were reproducible. With bronchoconstriction, frequency responders displayed greater hyperinflation and stronger breathing discomfort than volume responders (P<0.01). Analysis of the responses to induced bronchoconstriction disclosed distinctive and reproducible respiratory adjustments that may identify functionally different asthma subpopulations.
authors.affiliation: Department of Experimental and Clinical Medicine, Largo Brambilla 3, 50134 Florence, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Lavorini
authors.forename: Chiara
authors.initials: C
authors.lastname: Magni
authors.forename: Elisa
authors.initials: E
authors.lastname: Chellini
authors.forename: Gianna
authors.initials: G
authors.lastname: Camiciottoli
authors.forename: Massimo
authors.initials: M
authors.lastname: Pistolesi
authors.forename: Giovanni A
authors.initials: GA
authors.lastname: Fontana
mesh_terms: D000328:Adult; D001249:Asthma / Q000175:diagnosis / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D016084:Bronchoconstriction / Q000187:drug effects / Q000502:physiology*; D016085:Bronchoconstrictor Agents / Q000494:pharmacology; D004417:Dyspnea / Q000175:diagnosis / Q000209:etiology; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D010991:Plethysmography; D012123:Pulmonary Ventilation / Q000187:drug effects / Q000502:physiology*; D013990:Tidal Volume; D013997:Time Factors; D064232:Visual Analog Scale; D055815:Young Adult
chemical_list: D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride
keywords: Asthma; Breathing pattern; Bronchoconstriction; Control of breathing