Topical upper airway anaesthesia with lidocaine increases airway resistance by impairing glottic function.

OBJECTIVE

To assess if two different forms of upper airway topical anaesthesia induce similar changes in airway flow resistance (Rrs).

DESIGN

Serial measurements of Rrs before and after topical anaesthesia with acqueous or paste lidocaine.

SETTING

Lung function test laboratory.

PARTICIPANTS

9 normal men with documented normal lung function tests.

INTERVENTIONS: 2 different session of topical upper airway anaesthesia with 100 mg of liquid 5% lidocaine and 100 mg of 2% lidocaine paste, respectively.

MEASUREMENTS AND

RESULTS

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.

CONCLUSIONS

Topical upper airway anaesthesia transiently increases Rrs with no specific effects regarding the drug presentation. Laryngeal dysfunction may be one mechanisms involved in Rrs increase following upper airway topical anaesthesia. Such findings may explain some poor respiratory tolerance reported during endoscopy.