Expert commentary: Jackie Stephen-Haynes on 'How to...Top ten tips for doppler APBI'
21/11/11 | Assessment and diagnosis, Leg ulcers | Jackie Stephen-Haynes
There are a number of tips that can be very helpful when teaching registered clinicians about the accurate and safe measurement of Doppler ultrasound and the calculation of ankle brachial pressure index (ABPI).
It is essential to ascertain the patient's past medical history prior to the assessment in order to make an informed opinion about the likelihood of arterial or venous disease before measuring the ABPI. This can alert clinicians to the presence of operator errors and false readings. Clinicians should consider if the ABPI confirms what they already believed to be true. Caution should be taken when the past medical history, holistic assessment and the Doppler ultrasound results do not match.
Pain can create difficulties. If it is too painful for the patient to lie still for the time needed to undertake the Doppler assessment or if it is difficult to tolerate cuff inflation, it will not be possible to measure the ABPI. Careful consideration and planning of the Doppler ultrasound is necessary, as well as the appropriate use of analgesia.
We often encounter practical difficulties with the Doppler technique, especially in patients with chronic oedema and/or lymphoedema, where the normal signs of arterial disease may not be apparent. The volume of oedema in some patients may prevent the Doppler ultrasound from detecting any signal.In extremely swollen limbs, it might not even be possible to apply a cuff. On these occasions it is important to consider the following resources:
- Dupplex scan
- Larger cuff sizes
- Use of a lower frequency probe
- Measurement of toe/brachial pressure index instead.
The use of headphones (usually supplied with the Doppler ultrasound) can assist when it is hard to hear the pulses. It is important to use them throughout the procedure so that the ankle and brachial results are recorded consistently. A neck cord may also be worn, so that both hands are free for the procedure. The ABPI should be calculated using an electronic calculator rather than a chart, and the registered clinician should be sure to use the correct equation.
In my experience, the main causes of false readings are:
- Insufficient rest time
- Staff taking recordings too quickly because of time constraints
- Incorrect cuff size
- The cuff being repeatedly inflated for long periods
- The cuff being poorly secured around the ankle
- The cuff deflating too rapidly
- The vessels being calcified.
The advantage of an automatic system (ie, Dopplex® ABIlity; ArjoHuntleigh) is that they allow the recording of an ABPI within three minutes of the cuffs being applied. In addition no rest is needed before the test. The results are automatically calculated and are available as print-out labels.
In summary, with both manual and automatic techniques, caution should be exercised:
- Where the holistic assessment does not match the ABPI measurement
- In the presence of skin necrosis and amputation
- With the hand-held Doppler if signals are dampened or monophasic.
My final tip is to look after the Doppler ultrasound equipment by keeping it in good condition, having it serviced annually, always carrying a spare battery and always storing it in its appropriate carry case.
- Callam MJ, Ruckley C, Dale JJ, Harper DR. Hazards of compression treatment of the leg: an estimate from Scottish surgeons. BMJ 1987; 294: 929–31.
Jackie Stephen-Haynes, Visiting Professor in Tissue Viability, Professional Development Unit, Birmingham City University and Consultant Nurse, Worcestershire Health and Care NHS Trust, UK
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