TOPICAL UPPER AIRWAY ANESTHESIA WITH LIDOCAINE INCREASES AIRWAY-RESISTANCE BY IMPAIRING GLOTTIC FUNCTION

Objective: To assess if two different forms of upper airway topical an aesthesia induce similar changes in airway flow resistance (Rrs). Desi gn: Serial measurements of Rrs before and after topical anaesthesia wi th acqueous or paste lidocaine. Setting: Lung function test laboratory . Participants: 9 normal men with documented normal lung function test s. Interventions: 2 different session of topical upper airway anaesthe sia with 100 mg of liquid 5% lidocaine and 100 mg of 2% lidocaine past e, respectively. Measurements and results: Rrs was measured by the ran dom noise forced oscillation technique. Fiberoptic upper airway examin ation was performed in two subjects. Rrs increased on average by 81% a fter lidocaine spray and by 68% after lidocaine paste (p<0.005, respec tively) with no difference in the magnitude of Rrs increase between th e two modes of anaesthesia studied. This increase lasted 13+/-3 min (s pray) and 12+/-3 min (paste), respectively (p = ns). Fiberoptic examin ation 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. Laryngea l 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.