The bronchoprotective effect of deep inspiration is flow rate dependent.
OBJECTIVE
Deep inspiration (DI) protects against methacholine-induced bronchoconstriction in healthy subjects. We hypothesized that this bronchoprotective effect of DI depends upon the inspiratory flow rate.


METHODS
Prospective, controlled study.


METHODS
Pulmonary function laboratory within a large tertiary medical center.


METHODS
Ten healthy nonsmokers without asthma or rhinitis.


METHODS
First, we performed a methacholine challenge in the absence of DI to determine the concentration sufficient to reduce FEV(1) by 20%. On two subsequent days, the challenge was repeated with the addition of either a fast or slow DI immediately before the threshold concentration of methacholine. We calculated the % reduction in FEV(1) and FVC from baseline.


RESULTS
Mean % reduction in FEV(1) and FVC was significantly less with a fast DI than with no DI (20+/-3% vs. 34+/-4% for FEV(1), p=0.02; 12+/-3% vs. 23+/-3% for FVC, p=0.03); slow DIs did not significantly affect the methacholine-induced reduction in lung function.


CONCLUSIONS
A fast DI is bronchoprotective while a slow DI is not. Elucidating the conditions that maximize or alternatively, eliminate bronchoprotection in healthy subjects may ultimately provide insight into the pathophysiology of asthma.
Skloot
Gwen S
GS
Division of Pulmonary and Critical Care Medicine, Department of Medicine, The Mount Sinai School of Medicine, New York, NY 10029, USA. gwen.skloot@mssm.edu
Chandy
Dipak
D
Schachter
Neil
N
Togias
Alkis
A
D000328:Adult; D001985:Bronchial Provocation Tests; D016084:Bronchoconstriction / Q000502:physiology*; D016085:Bronchoconstrictor Agents; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D008297:Male; D016210:Methacholine Chloride; D011446:Prospective Studies; D014797:Vital Capacity / Q000502:physiology
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride