A doppler ultrasound is a non-invasive device that uses high-frequency sound waves to estimate the amount of blood flow through your arteries and veins, usually those that supply blood to your arms and legs. A doppler ultrasound can estimate how fast blood flows by measuring the rate of change in its pitch (frequency). For those who haven’t seen it before, an ultrasound gel is placed on the probe, also called a transducer, and then swept back and forth across a pulse point to locate and hear the distinctive sound of the blood flow.
Essentially, we use a doppler in class or when trying a new improvised tourniquet to establish cessation of blood flow. While during an actual event we would put the circumferential band of the tourniquet on as tight as possible and then twist the stick until all arterial blood flow has ceased, it’s nice in training to have a sense of how tight that is, how many turns, etc.
We use the Edan SonoTrax Vascular doppler 8 Mhz. They are available online new for as little as $120. It’s cheap, but seems to do the job. (Edan did not provide any support or product to Crisis Medicine.)