Cardiopulmonary effects of mechanical distension of the rumen in nonanesthetized sheep

The cardiopulmonary effects of mechanical distension of the rumen were studied in nonanesthetized sheep. Results in group I ewes indicated that simply increasing intraruminal pressure by compressed air insufflation did not seriously affect cardiopulmonary hemodynamics. Changes were more serious in group II ewes when water injection was followed by ruminal insufflation with compressed air. Heart rate, total peripheral resistance, and total pulmonary resistance increased, with a concommitant increase in arterial and pulmonary blood pressure and decrease in stroke volume. Infusion of water alone increased heart rate and cardiac output. The blood gas data indicated a definite arterial hypoxemia and hypercapnia, suggesting impaired ventilation during ruminal distension. The increase in total pulmonary resistance was thought to be due to alveolar hypoxia caused by a significant decrease in ventilation.