Objective of project is to investigate by means of both in vitro and in vivo experiments the flow characteristics in arteries contaning artificially induced stenotic obstructions. The characteristics of primary concern are: (!) the increased resistance to blood flow, as indicated by the pressure drop across the stenosis and (2) turbulence created by the stenosis and turbulence . induced effects, such as sound generation and velocity fluctuations, which are useful in the diagnosis of stenoses. The in vitro tests involve model stenoses having well defined geometries and studied under both steady and unsteady flow conditions. special attention will be given to the corr-elation between stenosis-generated turbulence, induced wall-vibrations, and transmitted sounds. The use of a Doppler ultrasonic flowmeter to supplement sound measurements for the transcutaneous detection of stenoses will be investigated. In vivo pressure drop experiments will be continued with artificial stenoses induced in the abdominal aorta of large canines. BIBLIOGRAPHIC REFERENCES: Young DF, Cholvin NR, Roth AC: Pressure drop across artificially induced stenoses in the femoral arteries of dogs. Circulation Res. 36: 735-743,1975. Kirkeeide RL. Young DF, Cholvin NR: Wall vibrations induced by flow through simulated stenoses in models and arteries. Proc. 28th Annual Confr. Engr. Biol. 17: 408 (abstract), 1975.