Why should legs not be crossed when taking Blood Pressure (BP)?

Why Legs Should Not Be Crossed When Taking Blood Pressure

Crossing legs during blood pressure measurement can artificially increase blood pressure readings by 8-10 mmHg systolic and 4-5 mmHg diastolic in hypertensive patients, potentially leading to misdiagnosis and inappropriate treatment. 1

Physiological Effects of Crossed Legs on BP Readings

When a patient crosses their legs at the knee during blood pressure measurement, several physiological changes occur:

1. Increased peripheral vascular resistance: Crossing legs compresses blood vessels in the lower extremities
2. Isometric muscle activity: The position requires sustained muscle contraction
3. Altered hemodynamics: Blood flow patterns change, affecting venous return

These changes can significantly impact blood pressure readings:

• In hypertensive patients: Systolic BP increases by 8-10 mmHg and diastolic by 4-5 mmHg 1, 2
• In normotensive individuals: Systolic BP increases by approximately 2-3 mmHg 1
• Some studies report even larger increases of approximately 10 mmHg systolic and 8 mmHg diastolic 3

Clinical Implications

This artificially elevated reading has serious clinical consequences:

• Misclassification of cardiovascular risk: Many patients may be incorrectly placed in higher risk categories 1
• Inappropriate medication initiation or adjustment: Treatment decisions based on falsely elevated readings
• Unnecessary follow-up testing: Leading to increased healthcare costs
• Patient anxiety: From falsely elevated readings

Proper BP Measurement Technique

The American Heart Association and ACC/AHA guidelines specifically recommend keeping legs uncrossed as one of the seven essential strategies for accurate BP measurement 4:

1. No conversation during measurement
2. Empty bladder before measurement
3. Use correct cuff size (80-100% of arm circumference)
4. Place BP cuff on bare arm
5. Support arm at heart level
6. Keep legs uncrossed
7. Support back and feet

The patient should be comfortably seated with back supported, both feet flat on the floor, and the arm supported at heart level 4. This position should be maintained throughout the measurement.

Special Considerations

• Pediatric patients: Guidelines for children also specify that feet should be uncrossed and flat on the floor during measurement 4
• Elderly or disabled patients: May need assistance to maintain proper positioning
• Consistency in measurement: Position should be standardized and mentioned in clinical documentation 3

Common Pitfalls to Avoid

1. Failing to check leg position: Always visually confirm that the patient's legs are uncrossed
2. Inconsistent positioning: Ensure the same position is used for serial measurements
3. Rushing the measurement: Allow the patient 3-5 minutes of rest in the proper position before measurement
4. Ignoring other positioning factors: Remember that arm position, back support, and bladder fullness also affect readings

Proper patient positioning with uncrossed legs is a simple yet critical component of accurate blood pressure measurement that can significantly impact diagnosis and treatment decisions.