Effects of repeated deep inspirations on recovery from methacholine-induced airway narrowing in normal subjects.
BACKGROUND
A single deep inspiration (DI) is known to be a potent bronchodilator but it is not known if repeated DI can accelerate sustained recovery from bronchoconstriction.


METHODS
We induced sustained bronchoconstriction using increasing concentrations of nebulized methacholine (Mch) during tidal breathing and assessed airway narrowing by measuring respiratory resistance (Rrs) using forced oscillation in six healthy subjects. On separate days we examined the effects of DI every 3 minutes and of prohibition of DI on recovery of Rrs for 30 minutes after the end of Mch nebulization.


RESULTS
Bronchoconstriction (Rrs approximately 150% above baseline) was induced. DI during recovery had a transient bronchodilator effect but no cumulative effect. At 30 minutes after end of nebulization (and 2 minutes after the last DI) Rrs was 87% above baseline compared to 93% above baseline when DI was prohibited.


CONCLUSIONS
Recovery from induced bronchoconstriction with methacholine was slow (approximately 2%/min) and not accelerated by frequent DI.
Watson
Ann
A
Respiratory Medicine, National Heart and Lung Institute, Faculty of Medicine, Imperial College, London, United Kingdom.
Ind
Philip
P
Pride
Neil
N
D000280:Administration, Inhalation; D000328:Adult; D000368:Aged; D000403:Airway Resistance / Q000187:drug effects / Q000502:physiology; D001980:Bronchi / Q000187:drug effects / Q000502:physiology; D001985:Bronchial Provocation Tests; D016084:Bronchoconstriction / Q000187:drug effects* / Q000502:physiology; D016085:Bronchoconstrictor Agents / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D006801:Humans; D001239:Inhalation / Q000187:drug effects* / Q000502:physiology; D016210:Methacholine Chloride / Q000008:administration & dosage / Q000494:pharmacology*; D008875:Middle Aged; D012143:Respiratory Physiological Phenomena / Q000187:drug effects
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride