What is a handheld continuous wave Doppler and how does it work?

A handheld Doppler (HHD) is a portable ultrasound device that emits continuous ultrasound waves to detect blood flow. The probe contains transmitting and receiving elements that emit ultrasound, which reflects off moving blood and returns to the probe. The reflected signal is converted to audible sound, with faster blood flow producing higher frequency sounds, allowing clinicians to assess vascular function at the bedside.

How does the Doppler probe generate and detect ultrasound signals?

The Doppler probe contains a transmitting element that emits ultrasound waves and a receiving element that detects reflected waves. Ultrasound reflects off moving blood at a frequency directly related to blood velocity. The probe then transduces this reflected signal into audible sound, enabling real-time assessment of blood flow velocity and vessel patency during physical examination.

What are the main clinical applications of handheld Doppler in vascular assessment?

The handheld Doppler is used to detect pulses, screen for peripheral arterial disease (PAD) using the ankle brachial pressure index (ABPI), and localize venous insufficiency. It serves as a routine bedside tool for assessing peripheral vascular disease, which commonly affects older adults and includes disease of peripheral arteries and veins.

Why is the relationship between blood velocity and Doppler sound frequency important?

The frequency of the reflected Doppler signal is directly proportional to blood velocity. Faster blood flow produces higher frequency sounds, while slower flow produces lower frequencies. This relationship allows clinicians to qualitatively assess blood flow patterns and detect abnormalities in vascular function during bedside examination without invasive testing.

What is peripheral vascular disease and who is most commonly affected?

Peripheral vascular disease (PVD) is a common condition affecting older adults that involves disease of peripheral arteries and veins. While history and physical examination provide diagnostic clues, Doppler ultrasound has become routine for bedside vascular assessment. The condition includes peripheral arterial disease and chronic venous insufficiency, both detectable with handheld Doppler technology.

How does continuous wave Doppler differ from other ultrasound techniques?

Continuous wave Doppler involves constant transmission and reception of ultrasound signals, allowing real-time detection of blood velocity changes. This continuous approach makes it ideal for handheld bedside use, enabling clinicians to quickly assess vascular function and detect abnormalities in peripheral arterial disease and chronic venous insufficiency without requiring advanced imaging equipment.

What information can clinicians obtain from the audible Doppler signal?

The audible Doppler signal provides qualitative information about blood flow velocity and vessel patency. Higher frequency sounds indicate faster blood flow, while lower frequencies suggest slower flow or obstruction. This auditory feedback helps clinicians detect pulses, identify areas of vascular compromise, and assess the severity of peripheral arterial disease or venous insufficiency during preliminary diagnosisprognosis through physical examination.

Peripheral Vascular Exam Using a Continuous Wave Doppler

0 views12:25 min

1. Preparation

Obtain a blood pressure cuff, an HHD machine, Doppler gel, and skin marker.
Wash hands prior to examining the patient.
Begin with the patient in a gown, lying comfortably supine on the exam table.

Human circulatory system diagram highlighting major arteries in arms and legs for anatomical study.
Figure 2. The major arteries of the upper and lower extremities.

2. Lower Extremity Arterial Assessment

For patients with weak or absent pulses by palpation, or historical risk factors for peripheral arterial disease (PAD), use the HHD to assess blood flow. Begin by applying gel in the expected area of the artery being investigated ( Figure 2).
Place the Doppler over the artery at a 45 degree angle to the skin, pointing cephalad. If the Doppler signal is not detected, slowly move the Doppler probe medially and laterally, as occasionally, the path of distal arteries can vary. Remember that a small percentage of people may have a congenitally absent dorsalis pedal (DP) artery.
If a signal is encountered, note the character of the sound wave produced. While some HHD have a screen or can print out the waveform to view, the shape can also be determined by listening. A normal arterial waveform in the lower extremity is triphasic (Figure 3). The first component of the wave occurs in systole and is generated by the rapid flow of blood toward the probe, generating a high frequency wave. At the end of systole and beginning of diastole, blood flow slows and reverses direction, resulting in a second, lower frequency wave. Finally, forward returns at the end of diastole, producing the low frequency third wave. Distal to an arterial stenosis, the amplitude of the waveform becomes progressively dampened with loss of flow reversal, resulting in a monophasic waveform. Immediately over a partially stenosed segment of artery, the flow velocity is increased, producing a high frequency wave. Complete arterial occlusion without collateral flow leads to absence of flow distally and no signal generation.

Blood flow dynamics graph; rapid systolic flow, early diastolic reversal, late diastolic flow.
Figure 3. The triphasic Doppler arterial waveform. The initial large deflection is forward blood flow during systole. The second deflection is the reversal of flow in early diastole. The third deflection is return of forward flow in late diastole.

If frequent reassessment is necessary, mark the location where the arterial pulse is found.
If there is suspicion for peripheral arterial disease based on the history or physical exam, calculate the ankle brachial pulse index (ABPI). Prior to performing the procedure, have the patient lie supine and relax for 10 min, with both the upper and lower extremities at the level of the heart.
1. Place the appropriately-sized blood pressure (BP) cuff on the upper arm. Make sure the cuff bladder length is at least 80% and the bladder width at least 40% of the arm circumference.
2. Apply gel to the antecubital fossa medial to the biceps tendon and find the brachial artery with the HHD.
3. Inflate the cuff until the Doppler signal disappears.
4. Slowly deflate the cuff. The first Doppler signal heard reflects the systolic pressure. Record this number and repeat the process in the other arm.
5. Place the appropriately sized BP cuff on the lower extremity, just proximal to the ankle.
6. Apply gel to the dorsum of the foot lateral to the extensor hallucis longus tendon and use the HHD to find the DP artery.
7. Inflate the cuff until the Doppler signal disappears.
8. Slowly deflate the cuff. The first Doppler signal heard reflects the systolic pressure. Record this number and repeat the process over the posterior tibialis (PT) artery.
9. Repeat this on the other leg.
10. Calculate the ABPI for a given leg by dividing the higher systolic pressure of the DP or PT artery in that leg with the higher of the two brachial artery systolic pressures. Table 1 shows the interpretation of the ABPI.

ABPI of leg A = Higher pedal pressure of leg A / Higher brachial pressure (A or B)
Value	Interpretation
>1.4	Non-compressible, calcified arteries
1.0-1.4	Normal range
0.91-0.99	Borderline
0.41-0.90	Mild to moderate peripheral arterial disease
<0.4	Severe peripheral arterial disease

Table 1: Interpretation of the Ankle Brachial Pressure Index (ABPI).

Assess for venous insufficiency of the lower extremity in patients with edema or varicose veins. Have the patient in the standing position with their weight shifted onto the unexamined leg.
1. Apply a generous amount of gel and place the HHD over the femoral artery, just below the inguinal ligament. Slowly move the probe medially, while squeezing and releasing the ipsilateral calf muscle to generate audible flow through the venous system. Once the HHD transmits this signal clearly, it is in the vicinity of the saphenofemoral junction (SFJ).
2. Move just inferior and medial to the SFJ to isolate the distal segment of the greater saphenous vein (GSV).
3. Squeeze the calf muscle and listen for normal augmentation of flow.
4. Release the calf muscle. Re-augmentation of flow lasting more than 1 sec is abnormal and represents retrograde flow through an incompetent valve at the SFJ.
5. Move to the medial thigh, approximately 10 cm above the knee along the expected path of the GSV, and apply gel.
6. Place the probe on the skin, while squeezing the calf muscle. The probe is well positioned once a clear signal is heard.
7. Squeeze the calf muscle and listen for normal augmentation of flow.
8. Release the calf muscle. Re-augmentation of flow lasting more than 1 sec may be heard with SFJ reflux, incompetent thigh perforator veins, or incompetent valves within the GSV proximal to the HHD probe.
9. Move behind the patient and place gel in the popliteal fossa.
10. Use the probe to find the popliteal artery, then move medially, while squeezing the calf muscle, to find the popliteal vein.
11. Once well-positioned over the popliteal vein, squeeze the calf muscle and listen for normal augmentation of flow.
12. Release the calf muscle. The venous anatomy around the popliteal fossa is complex, and re-augmentation of flow lasting more than 1 sec usually cannot be localized to one particular superficial or deep vein. Rather, it may represent reflux at the saphenopopliteal junction (SPJ), the small saphenous vein, tributaries of the GSV, or calf veins.