As a podiatrist, vascular examination is an essential skill for screening for Peripheral Arterial Disease (PAD) and assessing patients' circulatory status. Doppler is particularly useful for measuring Ankle-Brachial Index (ABI) and obtaining a clear view of arterial blood flow. This practical guide helps you integrate Doppler into your clinical routine, following the recommendations of the French National Authority for Health (HAS) in November 2020.
Doppler for the detection of PAD
PAD is a common condition in patients with cardiovascular risk factors such as diabetes, hypertension, or smoking. It reduces blood flow to the lower limbs, leading to serious complications, including the formation of ischemic wounds. As a podiatry professional, using Doppler allows you to:
- Objectively assess the arterial pulses of the lower limbs
- Detecting the first signs of arterial insufficiency
- Refer patients requiring additional medical follow-up
The steps of a rigorous vascular clinical examination
A complete vascular examination always precedes the use of Doppler and allows you to properly prepare the patient while refining your assessment:
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Inspection : Observe the feet and legs for signs of poor circulation such as pallor, cyanosis, hair loss, or ulcers. These signs are often indicative of vascular insufficiency.
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Palpation : Try to feel the pedal and tibial pulses. Although some pulses may be difficult to locate manually, this gives an initial indication of circulation.
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Doppler Auscultation : Place the Doppler probe on the superficial arteries to listen for blood flow. The device captures arterial signals and checks flow quality by identifying a biphasic or monophasic sound, a key indicator of blood circulation.
Calculation of the Ankle-Brachial Pressure Index (ABI) with Doppler
Calculating the ABI is fundamental for assessing the degree of arterial insufficiency in a patient. Here are the essential steps to perform this measurement using Doppler:
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Measure upper arm systolic pressure : Record the highest reading between the two arms using a traditional blood pressure monitor.
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Measure ankle systolic pressure : Use Doppler to detect the posterior tibial or pedal pulses, place a cuff around the ankle, and record the higher of the two pulses detected.
- Posterior tibial pulse: Place the probe just behind the internal malleolus of the ankle.
- Dorsal foot pulse (pedal pulse): Place the probe on the top of the foot between the big toe and the second toe.
Apply conductive gel to the Doppler probe. This gel is crucial to ensure good contact between the probe and the skin, allowing for efficient ultrasound transmission. Apply a sufficient amount of gel to the areas where you will be taking measurements. -
Calculating the ABI : Divide the ankle systolic pressure by the arm systolic pressure to obtain the ABI. The following are the interpretation thresholds:
- > 1.3 : Suspicion of incompressible arteries, common in diabetic patients
- 0.9 to 1.3 : Normal
- 0.8 to 0.9 : Well compensated AOMI
- 0.5 to 0.8: Moderately compensated AODI
- < 0.5 : Severe PAD or critical ischemia
Using IPS to guide wound management
The ABI also helps you better distinguish the origins of wounds. Ischemic wounds, for example, often appear in low-pressure areas (such as the toes or heel), with often black edges and cool surrounding skin. These indications can be used to refer the patient for further treatment if necessary.
Equipment Check
Before using the Doppler, check that the device is in good working order:
- Make sure the battery is fully charged.
- Clean the probe with a suitable disinfectant.
- Test the Doppler to ensure it is emitting ultrasound and displaying signals.
Doppler imaging, particularly with a suitable probe such as the 8 MHz probe, is invaluable for screening for PAD and assessing patients' vascular health. Through rigorous clinical examination and ABI measurement techniques, you play a crucial role in the early detection of vascular disease and contribute to the comprehensive and proactive management of at-risk patients.
Doppler Maintenance Tips:
- Clean the probe after each use to avoid cross-contamination.
- Store the device in a clean, dry place.
Safety Tips:
- Avoid using the device if you notice any signs of damage.
- Never apply excessive pressure to the probe, as this can impair the quality of the results and cause discomfort to the patient.
