Graduated compression therapy plays a major role in the treatment and prevention of varicose veins and leg ulcers, and the control of oedema. This therapy works by providing pressure and support for the superficial vessels. This counteracts the raised capillary pressure and prevents oedema.

Graded compression stockings exert a greater pressure at the ankle than at the thigh. This, therefore, provides a constant graded pressure and encourages the complete emptying of veins, decreasing venous pooling and venous stasis.

The amount of pressure required will depend on the size of the patient’s leg and the severity of the disease. However, ideally, the pressure should be no greater than that required to prevent capillary leakage.

Doppler assessment

Prior to the application of compression therapy, it is necessary to exclude arterial insufficiency. This is ensured by careful history taking, examination of the patient, and Doppler ultrasound assessment.

Doppler assessment is used to determine the Ankle Brachial Pressure Index (ABPI). This involves taking both the brachial and ankle systolic pressures using a hand-held Doppler probe to detect blood flow. The APBI is a comparison between the highest pressure at the ankle and the central systolic blood pressure i.e. the higher of the two brachial pressures (brachial pressures can vary between each arm).

In order that the Doppler assessment is accurate, it must be standardised with regard to equipment, environment and procedure. The following points must be considered:

• The cuff width should be 40% of the circumference of the midpoint of the limb, or 20% wider than the diameter.
• Bladder length should be twice its width. If the cuff is too narrow, this could result in an inaccurate high reading.
• Probe sizes vary. However, 5-8 MHz is normally used.
• The correct gel, in the correct quantity, should be applied in order that a good signal is heard.
• It must be recorded if the patient cannot lie down. This standardises the procedure and reduces the risk of the reading being falsely low due to exercise.
• Brachial systolic pressure should be measured in both arms and the higher reading recorded.
• The highest reading of at least two pulses on each leg should be recorded.
• Calcification of arteries can cause a false high reading . This can cause problems in individuals with diabetes (Vowden et al., 1996).

Calculating the ABPI

The patient should be supine and have been resting for 10-20 minutes prior to the assessment.

Brachial pressure

• Position the cuff around the upper arm.
• Palpate the brachial pulse and apply the ultrasound gel.
• Place Doppler at an angle of 45^o and locate the best signal.
• Arterial flow is a pulsating "woosh." Venous flow is a nonpulsatile rush.
• If difficulty is experienced in hearing arterial sounds, increasing the Doppler volume, adding more gel, and gently repositioning the probe will help.
• Inflate the cuff until the signal can no longer be heard. Slowly deflate the cuff and record the pressure at which the signal returns. Ensure that the probe is on the line of artery.
• Repeat the procedure for the other arm. Use the highest value to calculate the ABPI.

Ankle pressure

• Position the cuff around the ankle immediately above the malleoli (protect ulcer if present).
• Locate pulses by palpation or with the Doppler probe.
• Repeat as for brachial pressure reading.
• Record the ankle pressure as the highest reading of at least 2 pulses on each leg, such as the dorsalis pedis (felt between the first and second metatarsals) and the posterior tibial (felt behind the medial malleolus) pulse. Repeat for other leg (Vowden et al., 1996).

Points to remember when undertaking Doppler assessment

• Do not use any products other than Doppler conductive gel as they can damage the Doppler.
• If the probe is pressed to hard this can stop blood flow and eradicate the signal.
• After using the Doppler device, remove any gel from the probe and clean the tip with an aqueous solution. Alcohol or other disinfectants can cause damage. Remove any gel from the patients skin (McConnell 2000).

Doppler readings