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8 — Indirect Assessment of Arterial Disease
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The nature of the study should be explained to the patient and/or to an accompanying adult and an un- derstanding of the explanation should be document- ed as part of a departmental quality assurance plan.
A relevant PAOD history for lower extremities should include:
• The clinical problem, signs/symptoms, onset/ duration, and whether they are stable, improv- ing, or deteriorating
• The site and extent of intermittent claudication and the time for the symptoms to abate follow- ing the symptom-producing activity
• Coexisting clinical conditions: stroke/transient ischemic attack, carotid artery disease, heart attack, coronary artery disease, hypertension, diabetes, lipid disorder(s)
• Smoking history
• Family’s cardiac/peripheral vascular history
• Exercise activity
For the upper extremities, a similar history to that
for the lower extremity should be obtained, excluding intermittent claudication but including the following:
• Symptoms related to positional causes of arm
fatigue/numbness/aching
• Symptoms related to cold sensitivity
PATIENT POSITIONING
The examination table should be low enough for the patient to access safely, preferably without using a step stool. The ideal height for this is 22 inches to 24 inches, although this will then be too low for the comfort of the technologist (if standing throughout the test), so the exam table should be able to be elevated. Table width should be sufficient to avoid danger of the patient falling if rolled to a lateral de- cubitus position (which facilitates access at groin level, according to body habitus). For lower extrem- ity testing, the patient should be supine and the head should be raised slightly on a pillow so that the pa- tient is comfortable, but not so high that heart level is elevated. Legs should be rotated outward slightly, with the knees flexed, allowing access for the Dop- pler transducer to the popliteal artery.
When using volume plethysmography, the legs should be supported by placing a pillow under the heel to prevent the cuffs from being compressed by the bed, while being careful not to elevate it above heart level. To avoid artifacts from the effect of hydrostatic pressure, systolic pressures should be measured with the point of measurement at the same (horizontal) level as the heart.
For upper extremity testing, the patient position is similar to that for a lower extremity exam, but a pillow behind the knees will reduce back strain and enhance patient comfort. The arm should be abducted
slightly, supported on a pillow to ensure muscle re- laxation, but maintained at heart level—this is partic- ularly important when measuring systolic pressures.
Once the patient has been appropriately posi- tioned, the working height of the exam table should be adjusted (usually, between 28 inches and 32 inches) in accordance with the height of the tech- nologist. Table height can be lower when the exam is carried out with the technologist or sonographer in a sitting position, and this is an acceptable way of reducing back strain for the technical staff. To avoid positional injury to the staff when sitting throughout the study, the equipment should be able to be used without twisting or straining to reach a control. Us- ing a remote control to adjust equipment settings can enhance good ergonomics and may speed up obtain- ing results (although the technologist or sonographer will benefit from changing positions, during and fol- lowing the study).
SYSTOLIC PRESSURES
The measurement of systolic blood pressures in the limbs was one of the earliest noninvasive vascular studies performed. Since these early determinations, it was understood that relationships exist between pressure measurements recorded at various points along the arms and legs. Systolic pressures obtained correspond to the pressure in the vessels at the site of the blood pressure cuff and not to the vessels at the level of the transducer that is recording the pressure signals.
EXAMINATION TECHNIQUE
The test starts after 10 to 15 minutes of rest. This resting period allows the patient’s blood pressure to normalize in cases where the patient is initially anxious upon entering the examination room. The resting period also ensures peripheral blood flow will be at a resting level and not increased due to any hyperemia, which may have occurred as a result of walking into the testing facility. During this pe- riod, the appropriate documentation, as previously mentioned, is obtained.
Blood pressure cuffs are placed around the arms and legs. An appropriate cuff size is important in or- der to accurately measure blood pressure. The width of the cuff should be at least 20% wider than the di- ameter of the underlying limb segment.5 If the cuff is too narrow, a falsely elevated pressure will be mea- sured. Conversely, if the cuff is too wide, a falsely lower pressure will be measured. Using 12-cm cuffs for the brachial measurements is adequate in most patients, but the cuff may need to be wider according