BEAT TO BEAT REGULATION OF THE PULMONARY CIRCULATION IN CONSCIOUS DOGS. THE EFFECTS OF NORMAL RESPIRATION.
LOUVAIN UNIV (BELGIUM) CARDIOPULMONARY LAB
Pagination or Media Count:
In mongrel dogs, electromagnetic transducers were surgically implanted around the main pulmonary artery and at the root of the aorta. A week after the procedure, the effects of normal respiration on different parameters of the pulmonary circulation were investigated in healthy conscious animals. Mean pulmonary-left atrial pressure gradient PA-LA, right and left ventricular stroke volume SV, change in pulmonary-left heart central blood volume P-LH.CBV were monitored on a beat to beat basis at different times of the respiratory cycle. PA-LA mean pressure gradients only showed slight variations of .3 to 1.0 cm H20 with minimal values before and around peak inspiration. Right SV always increased during inspiration with maxima around peak inspiration while left SV showed similar variations with maxima occurring between the end of expiration and the inspiratory phase depending on the rate of breathing. P-L H. CBV changes up to 8 ml were observed during the respiratory cycle, their magnitude and exact timing varied with rates and depth of breathing. Beat to beat relationships between mean PA-LA gradient over right SV per second of ejection were used as an index of pulmonary vascular resistance PVR.
- Anatomy and Physiology