In segmental limb pressures, a technique called Doppler ultrasound is used to evaluate blood circulation in the major arteries in the arms or legs. A probe is passed lightly over different areas of your limbs, directing sound waves at particular arteries. The sound waves are reflected back at frequencies that correspond to the velocity of blood flow, and are converted into audible sounds and graphic recordings.
Segmental limb pressures are measured by combining Doppler ultrasound with blood pressure measurements at various locations in the arms and legs. By detecting differences in blood pressure at specific locations in different limbs, this test helps to diagnose arterial blockages and other circulation problems. It is most commonly performed in people suspected of having peripheral arterial disease (PAD), which is the narrowing of arteries in the legs due to the accumulation of plaques typically characterized by leg pain upon exercise.
Why have it done?
- To evaluate arterial blood flow in the arms or legs and detect blockages, trauma, or other circulation problems
- To aid in the diagnosis of PAD, determine the location of any arterial blockages, and determine the severity of functional impairment due to PAD
- To monitor the progression of known PAD and evaluate the effectiveness of treatments such as arterial bypass grafts in the legs
- To detect and evaluate possible arterial trauma.
- Blood pressure readings in the thigh may not be possible in obese patients, since a standard cuff may not be large enough to fit.
- Individuals with extremely calcified arteries may show falsely elevated ankle pressures. This is most common in people with diabetes, but may also be found in people on long-term corticosteroid therapy, kidney dialysis patients, and kidney transplant recipients.
How to prepare
- Avoid smoking for at least 30 minutes before the test as smoking constricts arteries and can interfere with the accuracy of the results.
- It is recommended to wear shorts and a short-sleeved shirt or a gown will be provided during the test.
What to expect
- While lying on an exam table, blood pressure cuffs are wrapped above the elbow on both arms. The cuffs are inflated, and blood pressure is measured in the artery on both sides.
- To examine segmental pressures in the legs, cuffs are then placed at various points at the thigh, calf, ankle, and foot. If the arms are being tested, cuffs are placed on the upper arms, forearm, and sometimes the hand or fingers.
- Each cuff is inflated in turn and blood pressures are measured at each site on the limb. This is done with the aid of an ultrasound transducer that is held against the skin.
- The test usually takes less than an hour.
Comparing the blood pressures at various locations in the legs can help to determine where arterial blockages are located, if any.