Confirming Diagnosis and Appropriate Treatment

The diagnosis of the ulcer should be made following a holistic assessment of the patient, which includes the history of the ulcer and patient, physical assessment and clinical presentation of the ulcer. An important part of this holistic assessment is the calculation of the ankle brachial pressure index (ABPI).

An ankle brachial pressure index (ABPI) involves the measurement of a person’s systolic blood pressure at their ankle and arm (brachial) using a Doppler machine. The ABPI provides an index of vessel competency by measuring the ratio of systolic blood pressure at the ankle to that in the arm, with a value of 1 being normal (NICE, 2015). Originally described by Winsor in 1950, this index was initially proposed for the non-invasive diagnosis of lower-extremity peripheral artery disease (PAD).

Blood pressure readings are taken from both arms, and the highest readings are used. Blood pressure readings are then taken using posterior tibial pulse and either the dorsalis pedis, anterior tibial or peroneal artery on each leg. The highest reading for each limb is then used to calculate the ABPI for each leg (Anderson, 2006).

Factors to consider when taking ABPI readings:

• Resting the patient – for 10 to 20 minutes in order to obtain a resting systolic pressure.
• Lying flat – ideally as flat as possible in order to reduce any hydrostatic pressure inaccuracies. If the patient is unable to do so the health care professional can bring their legs as near to heart level as possible and document this position to maintain consistency for future readings. If the patient is not lying flat, readings can be falsely high.
• Cuff size - ensure the appropriate size is used as the wrong one can result in accurate pressure readings.
• The probe – there are two sizes of probes: 8 MHz is the standard probe for use on normal limbs, and 5 MHz is a probe that can give better results for patients who are obese and for oedematous legs.

To measure the brachial systolic BP:

• Place an appropriately sized cuff around the upper arm.
• Locate the brachial pulse and apply ultrasound contact gel.
• Angle the Doppler probe at 45 degrees and move the probe to obtain the best signal.
• Inflate the cuff until the Doppler signal disappears, then deflate the cuff slowly and record the pressure at which the signal returns, taking care not to move the probe from the line of the artery or to apply too much pressure with the probe.
• Repeat the procedure for the other arm.
• Use the highest of the two values to calculate the ABPI.

To measure the ankle systolic BP:

• Place an appropriately sized cuff around the ankle immediately above the malleoli, having first protected any ulcer that may be present.
• Examine the foot, locating the dorsalis pedis or anterior tibial pulse and apply contact gel.
• Continue as for the brachial pressure, recording this pressure in the same way.
• Repeat this for the posterior tibial and, if required, the peroneal arteries.
• Use the highest reading obtained to calculate the ABPI for that leg.
• Repeat for the other leg.

(Adapted for Vowden, 2010; Whayman, 2014; Hodgman, 2016)

The ABPI, along with competent interpretation of clinical findings and history, will determine whether compression therapy will be safe to apply to the lower leg. Appropriate training is required due to the complexity of clinical reporting and methodological issues around interpretation and reproducibility of results (Caruana et al., 2005). Although this will not diagnose the ulcer, the ABPI will assist in determining the resting arterial pressure within the arteries.