Airway responses in normal subjects following topical anesthesia with ultrasonic aerosols of 4% lidocaine.

Airway dynamics were studied in seven healthy unanesthetized male subjects before and after topical anesthesia with ultrasonic aerosols of 4% lidocaine to assess the effects of this clinically useful technique on normal pulmonary function. Responses to the ultrasonic mist per se were evaluated by studies on separate days with physiologic saline. Significant increases in expiratory flow rates during maximal and partial expiratory flow-volume curves occurred in response to lidocaine. In contrast, flows during partial expiratory flow-volume curves were reduced following saline inhalation. Lung elastic recoil was unaffected by either aerosol. Results of single breath nitrogen washout and responses to breathing helium were unchanged following topical anesthesia with lidocaine, but the saline aerosol significantly increased the slope of phase III during nitrogen washout and volume of isoflow after breathing helium. These changes indicate that topical anesthesia of the airway with 4% lidocaine given as an ultrasonic aerosol produces mild bronchodilation in healthy subjects, whereas saline administered in the same fashion causes mild bronchoconstriction. The effects of both aerosols most likely represent direct action on the smaller peripheral bronchi.