Flow, pressure, and volume relationships in the pulmonary circulation during exercise in normal dogs and dogs with divided left pulmonary artery.

T HE object of this investigation was to measure simultaneous changes in blood pressure and blood flow in the pulmonary circulation of the intact dog. Observations were made during standing and running at different rates on a treadmill. A further group of dogs subjected recently to ligation and division of the left pulmonary artery was studied also. This permitted an extension of the observations in the presence of unusually high blood flow through a single lung. The pulmonary and left-heart blood volumes were measured simultaneously in an attempt to assess changes in the volume of blood in the lungs. Methods Preparation of Animals Ten mongrel dogs weighing 14 to 20.1 Kg. were taught to run on a horizontal treadmill at different speeds. Six dogs (nos. 1 to 6) were intact; and 4 (nos. 7 to 10) had been subjected to ligation and division of the left pulmonary artery 3 to 6 weeks previously. Two intact dogs were studied twice and one with a ligated and divided pulmonary artery (hereinafter referred to as "ligated pulmonary artery") was studied 3 times, making a total of 14 experiments. The dogs were trained to lie quietly supine while catheters were inserted under local procaine anesthesia with fluoroscopic and manometric guidance. A 40-cm. catheter (dead space, 0.4 ml.) was inserted via the common carotid artery into the left ventricle, and then the tip was withdrawn until it lay just above the aortic valve. Two 80-cm. catheters were inserted into an external jugular vein. One was advanced so that its tip lay in the From the Mayo Clinic and llayo Foundation, Boehester, Minn. The Mayo Foundation is a part of the Graduate School of the University of Minne-sota. pulmonary trunk just above the pulmonary valve, and the other was wedged into a distal pulmonary artery. Measurement of Pressure Statham strain-gage transducers were used to measure aortic, pulmonary-artery (PA), and pulmonary artery wedge (PAW) pressures. The zero reference point was midway between the dorsal and ventral aspects of the thorax when the dog was standing. In the process of recording, the pressures were electrically damped to minimize motion artefact and to produce mean values. At the beginning and end of each period of exercise the pressures were recorded undamped to confirm the positions of the catheter tips. Owing to changes in the dog's position during exercise, absolute PA and PAW pressures could not be measured accurately. However, …