ATTENUATION OF EXERCISE-INDUCED BRONCHOCONSTRICTION BY OROPHARYNGEAL ANESTHESIA

Abstract

To study the possibility that oropharyngeal receptors play a role in exercise-induced bronchoconstriction (EIB), 10 asthmatic children and adolescents with well-documented EIB were exercised on a treadmill for 10 min on 2 different occasions while breathing only through the mouth. The exercise load was sufficient to maintain each subject''s heart rate at 80-85% of maximum during the test. Before exercise, the posterior oropharynx of each subject was sprayed with either saline or 2% lidocaine in a random manner while the subject performed a breath-holding maneuver at the end of inspiration. Body plethysmography data, measurements of maximal expiratory flow-volume curves or both were obtained before and after aerosol administration, and again at 7 and 25 min after exercise. Although neither agent significantly changed the baseline pulmonary functions, lidocaine, when compared to saline, inhibited the decrease after exercise in forced vital capacity (P < 0.05), 1 s forced expiratory volume (P < 0.02) and forced expiratory flow during the middle half of the forced vital capacity (P < 0.01), and after exhalation of 50 (P < 0.02) and 75% of the vital capacity (P < 0.02). Lidocaine did not significantly inhibit the decrease in specific airway conductance (P < 0.20) after exercise. An examination of the individual subject data revealed a wide variation in the degree to which lidocaine inhibited EIB. Stimulation of the oropharynx during exercise probably contributes to the development of EIB through a reflex mechanism. Failure to prevent EIB completely in the subjects indicates that other mechanisms are involved in this phenomenon, irritant-like receptors are located elsewhere in the airways or both.