How do you measure blood pressure in the leg?

How to Measure Blood Pressure in the Leg

To measure blood pressure in the leg, the patient should be placed in a prone position if possible, with an appropriately sized thigh cuff placed midthigh, and the stethoscope positioned over the popliteal artery. 1

Proper Technique for Leg Blood Pressure Measurement

Patient Positioning

• Place the patient in a prone position when possible
• If prone positioning is not possible, a supine position with slight knee flexion can be used

Cuff Selection and Placement

• Use an appropriately sized cuff (typically a thigh cuff or oversized cuff)
• The bladder length should be 80-100% of the circumference of the thigh
• The bladder width should be at least 40% of thigh circumference
• Place the cuff midthigh with the bladder centered over the posterior thigh

Measurement Procedure

1. Allow the patient to rest for 3-5 minutes before measurement
2. Position the stethoscope over the popliteal artery (behind the knee)
3. Inflate the cuff 20-30 mm Hg above the point where the pulse disappears
4. Deflate at a rate of 2-3 mm Hg per second
5. Record the first Korotkoff sound as systolic pressure and the fifth Korotkoff sound as diastolic pressure
6. Take at least two measurements and average the results

Important Considerations

Normal Values

• Systolic blood pressure in the legs is typically 10-20% higher than brachial artery pressure 1
• A leg systolic pressure that is lower than arm pressure by >10 mm Hg may indicate coarctation of the aorta, especially in children 1

Clinical Applications

• Leg blood pressure measurement is particularly important in children with elevated arm blood pressure to screen for coarctation of the aorta 1
• In adults, comparing arm and leg pressures can help diagnose peripheral vascular disease

Common Pitfalls

• Using a cuff that is too small will falsely elevate blood pressure readings 2
• Improper positioning of the stethoscope may lead to inaccurate readings
• Failure to position the leg at heart level can cause measurement errors due to hydrostatic pressure effects 1
• Rapid deflation of the cuff (>2-3 mm Hg per second) can lead to underestimation of systolic and overestimation of diastolic pressure 1

Special Considerations

For Obese Patients

• For patients with very large thighs, standard thigh cuffs may not be adequate
• Consider using tronco-conically shaped cuffs for better fit on conical-shaped limbs 3
• If proper cuff fit cannot be achieved, alternative measurement sites may need to be considered

For Children

• Children should have leg blood pressure measured as a screen for coarctation of the aorta if they show elevated arm blood pressure on repeated measurements 1
• Use an appropriately sized cuff based on the child's thigh circumference
• For children, if Korotkoff sounds are heard to 0 mm Hg, the point at which the sound is muffled (phase IV Korotkoff) should be taken as the diastolic blood pressure 1

By following these guidelines, clinicians can obtain accurate blood pressure measurements in the leg, which are essential for proper diagnosis and management of various cardiovascular conditions that affect morbidity, mortality, and quality of life.