technique works by a principle that sound varies in pitch in relation to distance between sound source and listener: pitch is higher when distance is small, and pitch lowers as distance increases.

In this case, sound source is blood pumping through artery in rhythmic manner.

Handheld transducer picks up changes in sound frequency as blood flows and ebbs, and it amplifies them.

Instructions:

Apply coupling gel to transducer probe.

Turn Doppler flow meter on.

Touch probe to skin, holding probe perpendicular to artery.

A pulsatile whooshing sound indicates location of artery.

May need to rotate probe, but maintain contact with skin.

Do not push probe too hard or you will wipe out pulse.

Inflate cuff until sounds disappear; then proceed another 20 to 30 mm Hg beyond that point.

Slowly deflate cuff, noting point at which first whooshing sounds appear; this is systolic pressure.

Review: Health Assessment Vital Signs