The influence of upper respiratory tract receptors stimulation on the respiration and heart action in rats.

1. Stimulation of the upper respiratory tract with water releases reflex respiratory arrest and very marked bradycardia due to conduction and impulse generation disturbances in the heart accompanied by ventricular hyperexcitability. 2. Asphyxia causes bradycardia as a result of an inhibition of sinus node and the development of vicarious rhythms with excessive ectopic ventricular excitability. The intensity and duration of bradycardia during asphyxia are less than during water stimulation of airways. 3. Urethane anaesthesia did not prevent the development of the above described changes appearing during stimulation of the upper airways while topical analgesia with lidocaine completely prevented their appearance. The observations seem to suggest that for safety, surgical treatment in the upper airways should be done under analgesia of the respiratory mucosa. 4. The mechanism of the development of these changes seems to depend mainly on nervous and humoral factors, although the influence of other factors cannot be excluded. 5. Reflex changes in the action of the heart caused by water stimulation of the upper airways may be one of important components of the complex physiopathological process leading to death in drowning persons.