A technique for monitoring blood flow changes with miniaturized Doppler flow probes

A method for constructing miniaturized Doppler blood flow probes is presented. Since these probes weigh less than 100 mg and have crystal heads less than 0.5 mm in size, they are suitable for chronic placement on vessels as small as 200 micron. The probes are positioned under the vessel and rotated to optimize the Doppler signal. While held in that position, the crystal head is attached to the adventitia of the vessel with cyanoacrylate glue. A cuff holding the vessel and probe in the chosen position is then formed in situ by the application of a drop of silicone polymer. Data are presented showing the linearity of a flow probe response with the volume blood flow at rates as low as 14 microliter/min. With the use of the uterine artery of the conscious, unrestrained rat as an example, the probe was demonstrated to detect a dynamic change in flow.