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PART 4 — PERIPHERAL VENOUS
Classical compression techniques using an auto- matic system are recommended to alter venous flow. A pneumatic cuff is wrapped around the thigh or the calf. Testing is performed in veins centrally located in relation to the cuff.
A cuff around the upper calf often provides com- pression sufficient to test the veins from the groin to behind the knee. Even ankle veins can be evaluated with the cuff in this position. Normal flow in a vein proximal to the cuff should increase during compres- sion and should stop during decompression. Patho- logical flow or reflux occurs during decompression. Flow in a vein distal to the cuff should occur only during decompression. In this case, reflux would occur during compression.
Proper compression techniques using this cuff method require a pressure of 70 to 80 mm Hg to be applied quickly, held for a few seconds, and released quickly. Higher pressures may have to be applied to large extremities. The compressor must be filled withenoughairandthehosesmustbelargeenough, particularly if a large cuff is employed. The applied pressure may vary depending on the relative size of the cuff to the thigh or calf. The applied pressure de- creases significantly with tissue depth if a small cuff is used. Tissue pressure decreases as the distance between tissue or vein and the skin increases. Large cuffs apply pressure to the deep tissues and veins more uniformly.
Reflux duration is dependent on the vein filling with blood and the vein emptying with compres- sion. The duration of compression and the interval between compressions may affect reflux measure- ments. Sequential evaluations of reflux at multiple locations are also affected by compression duration and refilling time. As a standard, a minimum of 30 seconds between testing sites is recommended.
The automatic compression/decompression tech- nique (known as rapid cuff inflation/deflation) is commonly commanded with a foot switch. This re- lieves the hands of the technologist to concentrate on the transducer and instrument controls. It is also considered a reproducible, standardized technique.
The “parana maneuver” presents physiological advantages. This method involves a touch provoca- tion to force the patient to shift weight slightly for- ward and backward while the transducer interrogates the vein in real time. With skill and practice, the pa- rana maneuver is reproducible and may best reflect the patient’s own calf pump and valvular function.
Some examiners rely on hand compression, although this technique may introduce a large testing variability. A major justification is added variety of testing conditions. Unusual venous segments can be specifically tested. The amount and time of compres- sion can be readily adapted to different veins, different
anatomies, and different types of patients. Testing al- ternatives increase at the expense of consistency.
The Valsalva maneuver is commonly used to elicit reflux in the large, proximal veins of the lower extremity. Laughing, coughing, and talking are alter- natives to a Valsalva maneuver.
Usually, reflux duration is measured during de- compression of pressure applied distal to the site of measurement. Reflux time duration can also be measured under compression proximal to the site of observation. Reflux is then detected in a superficial vein as flow escapes to a different route in the pres- ence, for example, of venous obstruction of the main draining channel.
Traditionally, reflux time measurement is per- formed using the spectral Doppler with the vein in a longitudinal image. Documentation should include this standard method as usual protocol or as valida- tion of other methods used to detect reflux.
A greatly informative way of screening for reflux is with color flow transverse/oblique images. Multiple veins can be studied simultaneously. This technique is of great value while studying the great saphenous vein and one of its superficial tributaries at the lower thigh, for example. Another appropri- ate double vein evaluation is in the upper calf while observing reflux simultaneously in the GSV proper, or while differentiating the posterior and anterior arches or other tributaries. Recirculating reflux is particularly obvious while studying two veins simul- taneously with color flow. Reflux time can also be screened with spectral Doppler using a transverse/ oblique ultrasound image. Although this technique is adequate for detection of severe reflux, the report must validate such findings with spectral Doppler in longitudinal images.
PROTOCOL REQUIREMENTS
CVVI is concerned primarily with abnormal reverse flow, or reflux, in superficial (and deep) veins of the lower extremities. Given the scanning techniques described in the preceding section, images are ob- tained documenting B-mode characteristics, spectral Doppler waveforms, or color flow to demonstrate the following findings:
• Compressibility or coaptability of the femoro- popliteal veins at various levels, tested by man- ual compression with the transducer at the skin surface
• Patency and flow characteristics of the common femoral vein at one level, with color flow and spectral Doppler waveforms
• Patency and flow characteristics of the femoral vein at one or more levels, with color flow and spectral Doppler waveforms