Left atrial distension or increased left atrial pressure stimulated breathing frequency, an effect that was blocked by vagal cooling, suggesting it initiates reflex tachypnea.
Does increased left atrial pressure stimulate breathing frequency in anesthetized dogs?
Left atrial distension initiates reflex tachypnea in a canine model, mediated by vagal pathways.
Distension or loading of the isolated canine left heart caused reflex tachypnea in prior studies. The object of the present effort was to explore the possibility that this depended primarily on atrial distension. Cardiopulmonary bypass perfusion and ligation of pulmonary veins were used to isolate the left-heart chambers of anesthetized dogs. Simultaneous distension of the beating left atrium and fibrillating ventricle stimulated breathing frequency (f), whereas isolated ventricular distension did not. At other times, intervals of atrial fibrillation were imposed under two different conditions: 1) while the right heart and lungs were bypassed and systemic perfusion was provided by the left ventricle using blood returned to the left atrium by pump and 2) while the ventricles fibrillated and systemic perfusion was supplied directly by the pump. Atrial fibrillation increased left atrial pressure and stimulated f in condition 1. In condition 2, f increased only if fibrillation was associated with a rise in left atrial pressure. Vagal cooling blocked the effect of fibrillation. I conclude that left atrial distension may initiate reflex tachypnea.
T. C. Lloyd (Sat,) conducted a other in Anesthetized dogs. Left atrial distension / increased left atrial pressure vs. Isolated ventricular distension / baseline was evaluated on Breathing frequency (f). Left atrial distension or increased left atrial pressure stimulated breathing frequency, an effect that was blocked by vagal cooling, suggesting it initiates reflex tachypnea.