A DIFFERENTIAL BRONCHOMOTOR RESPONSE TO COOLING AND DRYING THE UPPER AIRWAY

The present study aimed to compare the reflex bronchoconstrictor effec ts of upper airway applications of dry airstreams with equivalent cool ing produced by cold isotonic and hypertonic saline solutions in anaes thetized rabbits. A method of on-line, breath by breath analysis of lu ng mechanics was used. The changes in total lung resistance (RL) and d ynamic lung compliance (Cdyn) produced by dry airstreams and by cold h ypertonic saline were greater than those induced by cold isotonic sali ne. Warm isotonic saline and supersaturated airstreams were ineffectiv e. These results implicate osmotic disturbances in the response to dry airstreams. The response to dry airflow was abolished by section of t he superior laryngeal nerves, by vagotomy and by atropine, suggesting a central cholinergic reflex mechanism is involved. Phosphoramidon had no effect, indicating that tachykinins are unlikely to play a role in this particular reflex.