title: Mechanical response to methacholine and deep inspiration in supine men.
abstract: The effects of supine posture on airway responses to inhaled methacholine and deep inspiration (DI) were studied in seven male volunteers. On a control day, subjects were in a seated position during both methacholine inhalation and lung function measurements. On a second occasion, the whole procedure was repeated with the subjects lying supine for the entire duration of the study. On a third occasion, methacholine was inhaled from the seated position and measurements were taken in a supine position. Finally, on a fourth occasion, methacholine was inhaled from the supine position and measurements were taken in the seated position. Going from sitting to supine position, the functional residual capacity decreased by approximately 1 liter in all subjects. When lung function measurements (pulmonary resistance, dynamic elastance, residual volume, and maximal flows) were taken in supine position, the response to methacholine was greater than at control, and this was associated with a greater dyspnea and a faster recovery of dynamic elastance after DI. By contrast, when methacholine was inhaled in supine position but measurements were taken in sitting position, the response to methacholine was similar to control day. These findings document the potential of the decrease in the operational lung volumes in eliciting or sustaining airflow obstruction in nocturnal asthma. It is speculated that the exaggerated response to methacholine in the supine posture may variably contribute to airway smooth muscle adaptation to short length, airway wall edema, and faster airway renarrowing after a large inflation.
authors.affiliation: Anestesia, Rianimazione e Medicina d'Urgenza, Azienda Ospedaliera S. Croce e Carle, Università di Genova, Genova, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Meinero
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Coletta
authors.forename: Luca
authors.initials: L
authors.lastname: Dutto
authors.forename: Manlio
authors.initials: M
authors.lastname: Milanese
authors.forename: Giorgio
authors.initials: G
authors.lastname: Nova
authors.forename: Andrea
authors.initials: A
authors.lastname: Sciolla
authors.forename: Riccardo
authors.initials: R
authors.lastname: Pellegrino
authors.forename: Vito
authors.initials: V
authors.lastname: Brusasco
mesh_terms: D000328:Adult; D000403:Airway Resistance / Q000187:drug effects / Q000502:physiology; D016084:Bronchoconstriction / Q000187:drug effects / Q000502:physiology; D016085:Bronchoconstrictor Agents / Q000494:pharmacology*; D004548:Elasticity / Q000187:drug effects; D006801:Humans; D001239:Inhalation / Q000187:drug effects* / Q000502:physiology; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology*; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000187:drug effects* / Q000502:physiology; D016683:Supine Position / Q000502:physiology; D014109:Total Lung Capacity / Q000187:drug effects / Q000502:physiology
chemical_list: D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride