Areas on the body where blood pressure can be measured

Measurement of the blood pressure in various arteries is very useful in the evaluation of peripheral arterial disease. A blood pressure cuff is wrapped around the affected limb, and a Doppler ultrasound probe is placed on the skin over the artery. A doctor or examiner inflates the pressure cuff to a pressure high enough that the pulse is no longer heard with the Doppler and then slowly deflates the cuff. The pressure measured by the cuff when the arterial pulse is heard again is the arterial pressure under the cuff. These measurements can be taken at the ankle, toe, points on the leg (upper thigh, above the knee, upper calf), and points on the arm (elbow, forearm, wrist) or by inserting a catheter into an artery.

Ankle pressure

In most people, the resting ankle pressure is greater than the pressure at the crook of the arm, known as the brachial blood pressure. The ratio of the ankle pressure to the brachial pressure is called the ankle-brachial index (ABI). A normal ABI is 0.9 to 1.3. A person with an ABI less than 0.9 may have peripheral arterial disease.

Toe pressure

Toe pressures can be measured with miniature blood pressure cuffs. In general, a toe pressure measuring less than 30 millimeters of mercury (mm Hg) means that the person has severe arterial insufficiency at the level of the toes.

Segmental leg pressures

Arterial pressure can be estimated in the upper thigh, above the knee, and in the upper calf by placing blood pressure cuffs at the appropriate levels. The pressures can be compared between the two legs or at different levels in the same leg.

Arm pressures

Blood pressures can be measured at the elbow (brachial), forearm, or wrist. Large differences between pressures at the various levels suggest arterial blockage. As with toes, finger pressures can be measured. And a finger-brachial index can be calculated. Finger-brachial ratios of less than 0.8 suggest that a person has arterial disease of the upper extremity.

Invasive blood pressure measurements

The blood pressure in a person's arteries can be directly measured using catheters placed in the arteries that are being studied. Because the arteries are punctured, this is known as invasive blood pressure monitoring. The results can be interpreted in a way similar to the noninvasive blood pressure measurements.

Last Updated: October 16, 2009

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