Portable directional ultrasonic Doppler blood velocimeter for ambulatory use.

The design of a portable directional Doppler velocimeter and of purpose-built probes intended for monitoring blood flow in femorodistal bypass grafts in ambulatory patients are described. The design is based on a continuous-wave Doppler technique with quadrature demodulation. The Doppler unit was interfaced to a 'personal-stereo' recorder to store the Doppler signals. The advantages and the limitations of recording flow in ambulatory patients are discussed. Examples of blood flow data collected from femorodistal bypass grafts are given.