Vomiting: Radiographic and Oscillographic Correlates in the Decerebrate Cat

Emesis was evoked in unanesthetized cats by the administration of veratrum alkaloids (50 to 100 μg per kg intramuscularly). Visceral pressure changes, measured via thoracic and abdominal venous catheters, were temporally compared with cineradiographic records of retching and expulsion. Repeated thoracic herniations of the abdominal esophagus and cardiac portion of the stomach coincided with negative thoracic pulses which characterized retching. Contrast material from the stomach moved freely to and fro into a dilated esophagus during retching, and the maximum retrograde movement of material lagged the peak negative pressure by about 300 msec. Expulsion was typified by a final reversal of thoracic pressure from negative to positive. It began with the cardia already situated in the thorax as the result of the preceding retching. The expulsive event was accompanied by a rapid anterior displacement of the diaphragm accomplished within two to four cineradiographic frames (67 to 134 msec). Retching, then, is basically a preparatory maneuver in which respiratory mechanisms are used to defeat the inherent antireflux characteristics of the abdominal esophagus and cardia prior to expulsion.