Blood Pressure in the Calf Vs. the Arm

A healthy blood pressure (BP) ensures adequate blood supply to important organs, and is an important indicator of heart health. While arm BP measurement is the standard practice, calf BP (also called ankle BP) may be appropriate in certain situations.

Units

• Examiners typically provide blood pressure (BP) as two numbers, both in "millimeters of mercury" (mm Hg). The first number (systolic pressure) indicates the pressure of blood flow during the heartbeat, while the second number (diastolic pressure) reflects the blood pressure between two heartbeats.

Common Equipment

• Common instruments for BP measurement include a stethoscope and a manual or stand-alone digital sphygmomanometer. The components of a phygmomanometer are an inflatable cuff; a manometer (pressure gauge) and a hand bulb with a pressure-control valve.

BP Measurement in the Arm

• For BP measurement in the arm, the patient usually sits, with the upper arm at approximately heart level. The examiner then applies the proper BP cuff size to the arm and estimates the pressure by palpating or by listening over the brachial artery with a stethoscope.

BP Measurement in the Calf

• For calf BP measurement, the patient lies on his or her back. The examiner then applies an appropriate cuff size to the calf, and estimates pressure by palpating, or by auscultating over the dorsalis pedis or posterior tibial artery (foot arteries).

Sources of Error

• According to World Anesthesia Online, most measurement errors result from the use of the wrong size of cuff. Body position can also affect readings.

Considerations

• The American Association of Critical Nurses (AACN) notes that calf BP readings differ from arm BP in an unpredictable manner. The AACN advises that examiners use calf BP only if the patient's upper arm and forearm are not accessible, or if no appropriate cuff size is available.