Plethysmography and impulse oscillometry assessment of tiotropium and ipratropium bromide; a randomized, double-blind, placebo-controlled, cross-over study in healthy subjects.

Aims: Spirometry, plethysmography and impulse oscillometry (IOS) measure different aspects of lung function. These methods have not been compared for their ability to assess long- and short-acting anticholinergic agents. We therefore performed a double-blind, placebo-controlled, four-way cross-over study in 30 healthy subjects.