title: Enhanced airway dilation by positive-pressure inflation of the lungs compared with active deep inspiration in patients with asthma.
abstract: Deep inspiration temporarily reduces induced airways obstruction in healthy subjects. This bronchodilatory effect of deep inspiration is impaired in asthma. Passive machine-assisted lung inflation may augment bronchodilation compared with an active deep inspiration in patients with asthma by either opening closed airways or by reducing fluid flux across the airway wall during deep inspiration, and thereby increasing the tethering forces on the airway wall. We recruited 24 patients with asthma [18-46 yr old, forced expiratory volume in 1 s (FEV(1)) > 70% predicted; provocative concentration of methacholine inducing a 20% fall in FEV(1) (PC(20)) < 8 mg/ml], with either an impaired (n = 12) or an intact (n = 12) bronchodilatory response to deep inspiration. Two methacholine challenges were performed on separate days. At a 50% increase in respiratory resistance (forced oscillation technique at 8 Hz), the change in resistance by a positive-pressure inflation (computer-driven syringe) or an active deep inspiration was measured in randomized order. The reduction in resistance by positive-pressure inflation was significantly greater than by active deep inspiration in the impaired deep inspiration response group (mean change +/- SE: -0.6 +/- 0.1 vs. -0.03 +/- 0.2 cmH(2)O.l(-1).s, P = 0.002). No significant difference was found between positive-pressure inflation and active deep inspiration in the intact deep inspiration response group (-0.6 +/- 0.2 vs. -1.0 +/- 0.3 cmH(2)O.l(-1).s, P = 0.18). Positive-pressure inflation of the lungs can significantly enhance deep inspiration-induced bronchodilation in patients with asthma.
authors.affiliation: Dept. of Pulmonology, Leiden Univ. Medical Center, PO Box 9600, NL-2300 RC, Leiden, The Netherlands. A.M.Slats@lumc.nl
authors.forename: Annelies M
authors.initials: AM
authors.lastname: Slats
authors.forename: Kirsten
authors.initials: K
authors.lastname: Janssen
authors.forename: Ronald C
authors.initials: RC
authors.lastname: de Jeu
authors.forename: Dirk T
authors.initials: DT
authors.lastname: van der Plas
authors.forename: Robert
authors.initials: R
authors.lastname: Schot
authors.forename: Joost G
authors.initials: JG
authors.lastname: van den Aardweg
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Sterk
mesh_terms: D000328:Adult; D000403:Airway Resistance / Q000187:drug effects / Q000502:physiology; D001187:Artificial Organs; D001249:Asthma / Q000503:physiopathology*; D001980:Bronchi / Q000033:anatomy & histology* / Q000503:physiopathology*; D001993:Bronchodilator Agents / Q000008:administration & dosage / Q000494:pharmacology; D035641:Chest Wall Oscillation; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D016210:Methacholine Chloride / Q000008:administration & dosage / Q000494:pharmacology; D011175:Positive-Pressure Respiration; D012121:Respiration, Artificial; D015656:Respiratory Mechanics / Q000502:physiology*; D055815:Young Adult
chemical_list: D001993:Bronchodilator Agents; D016210:Methacholine Chloride