Cleveland Family Study
9.2 General Methods
9.2.1 Using the Doppler
- For the Doppler probe to remain in proper condition, NEVER use ECG paste or cream as the medium between the skin and the crystals. Use AQUASONIC or any gel made for ultrasonic physical therapy equipment. In an emergency use any surgical jelly or lubricant, even Vaseline or mineral oil. After use, remove the gel with a soft tissue. If the probe has dried gel on it, wash it off under running water. Do NOT scrape off the gel.
- To preserve the battery, turn off the unit immediately after measurements. It takes less than a minute to make a blood pressure measurement. Turn off the unit immediately after removing it from the skin.
- The Doppler unit is operated by pushing the button on the unit to turn it on, and gradually turning the volume up. The probe is then placed over the artery (brachial or posterior tibial). The brachial artery is at the crease of the elbow, slightly toward the body. The posterior tibial artery is behind the inside ankle bone.
- The frequency is 8 Megahertz (vibrations of 8 million times per second). In order to hear the signal above background noise, the instrument must be pushed in toward the artery. Angling the beam upstream improves the signal. For deeper vessels, the unit will have to be tilted back toward perpendicular, but NOTE that the instrument works poorly or not at all if held fully perpendicular to the flow.
- On occasion there are unusual noises from the Doppler that do not indicate a problem with the Doppler. The normal sound will become obvious with experience in performing this test.
- Please note that the Doppler unit turns itself off after 5 minutes automatically. This may occur in the middle of a measurement.
- The purpose of the Doppler is to determine that blood is or is not flowing under the cuff. For correct interpretation, the probe MUST be centered directly over the artery and must not be moved while inflating the cuff.
- In some places along the posterior tibial artery there is anatomical hiding of the vessel by muscle or tendons. Move up or down the vessel a little to find the best signal above background noise.