['To assess if two different forms of upper airway topical anaesthesia induce similar changes in airway flow resistance (Rrs).', 'Serial measurements of Rrs before and after topical anaesthesia with acqueous or paste lidocaine.', 'Lung function test laboratory.', '9 normal men with documented normal lung function tests.', '2 different session of topical upper airway anaesthesia with 100 mg of liquid 5% lidocaine and 100 mg of 2% lidocaine paste, respectively.', 'Rrs was measured by the random noise forced oscillation technique. Fiberoptic upper airway examination was performed in two subjects. Rrs increased on average by 81% after lidocaine spray and by 68% after lidocaine paste (p < 0.005, respectively) with no difference in the magnitude of Rrs increase between the two modes of anaesthesia studied. This increase lasted 13 +/- 3 min (spray) and 12 +/- 3 min (paste), respectively (p = ns). Fiberoptic examination of the two most responders showed inspiratory laryngeal collapse.'] Does topical upper airway anaesthesia with lidocaine increase airway resistance by impairing glottic function?