[Vasal flow measurements at the aorta ascendens using the ultrasonic doubler technique in chronic experiments on rabbits].

The conditions under which flow measurements using the ultrasonic doppler technique can be successfully carried out at the Aorta ascendens in chronical experiments were studied in 25 normal rabbits. Pressure necroses of the vascular wall at agar-agar-gel coupling arise only if the implanted pick-off with its inner diameter is less than the outer diameter of the aorta + about 10%. The ultrasonic intensity permissible in a chronic experiment is only about 0.3 W/cm2. With the 13 implantations the animals were maximally usable for 86.6 days; 70% of them were killed in good health. In a beat-to-beat analysis were determined: (1) heart rate, (2) discharge duration, (3) maximal rate of discharge, (4) acceleration of blood flow, (5) deceleration of blood flow, (6) beat volume, (7) contraction force of the left ventricle, and (8) discharge resistance. The control recordings obtained over several months are on the average within normal limits.