Blood Pressure: Lower Extremity (Home Health Care) - CE/NCPD

ALERT

Blood pressure (BP) measurements with an electronic BP device may be affected by excessive movement, such as with seizures, tremors, or shivering, and by irregular heart rates.

OVERVIEW

BP is the force exerted by blood against the vessel walls. During a normal cardiac cycle, BP reaches a peak, which is followed by a trough. The peak pressure occurs when the heart’s ventricular contraction, or systole, forces blood under high pressure into the aorta. When the ventricles relax, the blood remaining in the arteries exerts a trough, or diastolic, pressure against the arterial wall. Diastolic pressure is the minimum pressure exerted against the arterial wall.

Patients at risk for alterations in BP measurement include those who have:

• Circulatory shock (hypovolemic, septic, cardiogenic, or neurogenic)
• Acute or chronic pain
• Rapid IV infusion of fluids or blood products
• Increased intracranial pressure
• Postoperative status
• Preeclampsia of pregnancy

The standard unit for measuring BP is millimeters of mercury (mm Hg). The measurement indicates the height at which BP can sustain the column of mercury.

The most common techniques for measuring BP are auscultation, using a sphygmomanometer and stethoscope, and measurement using an electronic BP monitor. Palpation may be used to obtain an estimate of systolic BP before using the auscultation method.

During auscultation, as the sphygmomanometer cuff is deflated, five different sounds, called Korotkoff sounds, are heard over the artery. Each sound has a distinct characteristic (Figure 1). BP is recorded with the first Korotkoff sound (systolic pressure reading) and at the beginning of the fifth Korotkoff sound (diastolic pressure reading). The difference between systolic pressure and diastolic pressure is the pulse pressure. For a BP of 120/80 mm Hg, the pulse pressure is 40 mm Hg, the difference between 120 mm Hg and 80 mm Hg. Systolic BP readings tend to be higher in more distal arteries, whereas diastolic BP readings tend to be lower in more distal arteries.^{undefined#ref4">4,6}

The thigh or lower calf/ankle is used if measurement of the upper arms and forearms is not possible.⁸ Ankle blood pressure is clinically effective in diagnosing hypertension when the upper arm is not available for proper cuff placement.⁷

Cuff size should be proportionate to the limb circumference (Table 1). An improperly sized cuff produces an inaccurate BP measurement. Using a cuff that is too narrow results in an overestimation of BP, whereas using a cuff that is too wide results in an underestimation of BP.⁴ Most adults require a large adult cuff, particularly when the cuff is used for taking BP in a lower extremity.⁴ The correct cuff size is especially important for obtaining accurate readings in pediatric patients and patients with obesity.⁶

SUPPLIES

See Supplies tab at the top of the page.

EDUCATION

• Provide developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, and overall neurologic and psychosocial state.
• Explain how the equipment works as well as the procedure to the patient, family, and caregivers.
• Instruct the patient, family, and caregivers about ambulatory BP threshold guidelines. In adults, normal BP is less than 120/80 mm Hg (Table 2).^2,3
• Educate the patient, family, and caregivers about the signs and symptoms of hypotension (in adults, hypotension is considered a BP less than 90/60, although low BP without signs or symptoms is usually not treated):⁵
  • Dizziness or light-headedness
  • Fainting (syncope)
  • Blurred vision
  • Nausea
  • Fatigue
  • Lack of concentration
• Educate the patient, family, and caregivers about the risk factors for hypertension:
  • Family history of hypertension, premature heart disease, lipidemia, or renal disease
  • Obesity
  • Cigarette smoking
  • Vaping
  • Heavy alcohol consumption
  • High blood cholesterol and triglyceride levels
  • Prolonged stress from psychosocial and environmental factors
  • Sedentary lifestyle
• Educate the patient, family, and caregivers regarding the primary strategies for preventing hypertension:¹
  • Managing weight
  • Engaging in daily exercise
  • Limiting sodium and saturated fat in the diet
  • Taking medications as prescribed
  • Maintaining adequate intake of dietary potassium and calcium
  • Limiting alcohol intake
  • Avoiding tobacco products
• Instruct the patient, family, and caregivers to ensure that the patient has adequate rest before BP measurements and that BP measurements are performed at the same time each day using the same limb with the patient in the same position, either prone or supine.
• Explain to the family and caregivers that the patient must remain still and quiet during the procedure.
• Explain that Korotkoff sounds may be difficult to hear for one of the following reasons (Table 3):
  • Cuff is too loose, not big enough, or too narrow.
  • Stethoscope is not over the arterial pulse.
  • Cuff is deflated too quickly or too slowly.
  • Cuff is not inflated high enough for systolic readings.
• Encourage questions and answer them as they arise.

PROCEDURE

1. Perform hand hygiene and don gloves. Don additional personal protective equipment (PPE) based on the patient’s need for isolation precautions or the risk of exposure to bodily fluids.
2. Introduce yourself to the patient, family, and caregivers.
3. Verify the correct patient using two identifiers.
4. Explain the procedure to the patient, family, and caregivers and ensure that the patient agrees to treatment.
5. Verify the practitioner’s order and assess the patient for pain.
6. Prepare an area in a clean, convenient location and assemble the necessary supplies.
7. Review the patient’s medical record for a history of hypertension, cardiovascular disease, renal disease, diabetes, and other factors that may influence BP (e.g., weight, smoking, vaping, medications).
8. Evaluate the patient for signs and symptoms of BP alterations.
   1. Observe a patient at risk for high BP for:
      1. Headache (usually occipital)
      2. Facial flushing
      3. Nosebleed
      4. Fatigue
   2. Observe a patient at risk for low BP for:
      1. Dizziness
      2. Mental confusion
      3. Restlessness
      4. Pale, dusky, or cyanotic skin and mucous membranes
      5. Cool, mottled skin over the extremities
9. Determine the best site for obtaining a BP measurement. Avoid applying the cuff to an extremity in these situations:
   1. The extremity has been traumatized.
   2. The extremity has known infections or medical conditions (e.g., those causing vasoconstriction or a tumor pressing on the vascular supply, wounds, or lymphedema wrappings).
   3. The extremity has a cast or bulky bandage.
10. Determine the previous baseline BP and measurement site, if available, from the patient’s record.
11. Make sure the patient has not exercised, ingested caffeine, or smoked for 30 minutes before obtaining a BP measurement.² Make sure the patient does not have to void.

    Rationale: A full bladder increases pressure on the kidneys and can increase blood pressure.

12. Make sure the room is warm (approximately 22°C to 23°C [71.6°F to 73.4°F]).⁴

    Rationale: Exposure to cold can increase systolic BP.

13. Measure the leg circumference and select the appropriate-size cuff (Table 1).

    Rationale: Proper cuff size is necessary for an accurate reading. The cuff must be wide and long enough to allow for the size of the thigh. A narrow cuff can cause an artificially high reading.

14. Tell the patient that BP is going to be taken and that the cuff will squeeze the leg.
15. Expose the patient’s leg fully by removing any constricting clothing. Do not place the BP cuff over clothing.

    Rationale: Placing the cuff over clothing may affect the BP measurement.

16. Assist the patient to a prone position. If the patient is unable to assume a prone position, assist the patient to a supine position with the knee slightly flexed. Ask the patient not to cross the legs.

    Rationale: The prone position provides the best access to the popliteal artery. Leg crossing can falsely increase systolic and diastolic BP.

17. Apply the BP cuff.
    1. Thigh
       1. Palpate the popliteal artery for a pulse.
       2. Position the cuff over the lower third of the patient’s thigh.⁴
       3. Apply the cuff over the popliteal artery and above the popliteal fossa. If the cuff has no center arrows, estimate the center of the bladder and place it over the artery.

          Rationale: Positioning the cuff bladder directly over the popliteal artery ensures that proper pressure is applied during inflation.

       4. Wrap the fully deflated cuff evenly and snugly around the patient’s thigh.

          Rationale: A loose-fitting cuff can cause an artificially high reading.

    2. Lower calf/ankle
       1. Palpate the dorsalis pedis or posterior tibial artery for a pulse.
       2. Position the cuff over the lower half of the patient’s calf.⁸
       3. Secure the deflated cuff evenly and snugly around the lower calf and above the malleoli.
18. Position the manometer vertically at eye level.

    Rationale: Looking up or down at the scale can result in incorrect readings.

19. Ask the patient not to speak while BP is being measured.
20. Place the stethoscope earpieces in the ears and make sure sounds are clear, not muffled.
21. Locate the popliteal artery for thigh BP or the dorsalis pedis or posterior tibial artery for calf BP and place either the bell or the diaphragm of the stethoscope over the artery below the cuff’s lower edge.
    1. Do not allow the chest piece to touch the cuff or clothing.
    2. Do not place the diaphragm under the cuff.

       Rationale: Proper stethoscope placement ensures the best sound reception. An improperly positioned stethoscope can cause muffled sounds that often result in false-low systolic and false-high diastolic readings.

22. Turn the valve of the pressure bulb clockwise until tight. Quickly inflate the cuff above the patient’s previously documented systolic pressure or the point at which Korotkoff sounds cease.

    Rationale: Closing the valve prevents air leak during inflation. Rapid cuff inflation ensures accurate measurement of systolic pressure.

23. Slowly release the pressure bulb valve, allowing the manometer needle to fall slowly and continuously at a rate of 2 to 3 mm Hg per second.⁴

    Rationale: Too rapid a decline in the mercury level can cause an inaccurate measurement. Too slow a decline in the mercury level causes discomfort.

24. Observe the point on the manometer at which the first Korotkoff sound is heard, indicating the systolic BP. The sound slowly increases in intensity.

    Rationale: The first Korotkoff sound is a snapping sound. This sound for at least two consecutive heartbeats reflects the systolic BP.

25. Continue to deflate the cuff gradually; observe the point on the manometer at which all Korotkoff sounds disappear, indicating the diastolic BP.

    Rationale: The fifth Korotkoff sound falls silent as the cuff pressure drops below the diastolic pressure. Thus, the beginning of the fifth Korotkoff sound indicates diastolic pressure in adults.⁴

26. When the sounds disappear, quickly deflate the cuff completely.
27. Remove the cuff from the patient’s leg unless a repeat measurement is needed (after a brief pause).

    Rationale: Extended cuff inflation can cause arterial occlusion, resulting in numbness and tingling in the patient’s leg.

28. If this is the patient’s first BP measurement, repeat the procedure on the other leg.

    Rationale: Comparing BP in both legs helps detect circulatory problems.

29. Inspect the leg for any injury caused by cuff inflation before replacing clothing.
30. Help the patient resume a comfortable position and cover the leg if previously clothed. Inform the patient of the BP measurement, as appropriate.
31. Record abnormal values in the health record and report them to the practitioner (Table 2).
32. Clean the BP cuff per the manufacturer’s instructions and the organization’s practice. Clean the earpieces and diaphragm of the stethoscope with an alcohol swab or per the organization’s practice.
33. If obtaining a patient’s leg BP measurement for the first time, establish the BP reading as the baseline if it is within the acceptable range.
34. Compare the leg BP reading with the patient’s previous leg baseline, if available, and the usual BP for the patient’s age.
35. Discard or store supplies, remove PPE, and perform hand hygiene.
36. Document the procedure in the patient’s record.

EXPECTED OUTCOMES

• BP is within acceptable range.
• Patient tolerates procedure.

UNEXPECTED OUTCOMES

• BP is above or below acceptable range.
• BP is below acceptable range or insufficient for adequate perfusion and oxygenation of tissues.
• BP reading cannot be obtained.
• A significant difference exists between left leg and right leg BP readings.

DOCUMENTATION

• BP measurement
• Method used to obtain BP
• Site of BP measurement and patient’s position
• Signs and symptoms of BP alterations
• Abnormal findings
• Education
• Patient’s progress toward goals
• Unexpected outcomes and related interventions
• Assessment of pain, treatment if necessary, and reassessment

OLDER ADULT CONSIDERATIONS

• Older adults’ skin is more fragile and susceptible to damage from cuff pressure when BP measurements are frequent. More frequent evaluation of the skin under the cuff or rotation of BP sites is recommended.
• Older adults have increased systolic pressure related to decreased vessel elasticity.
• Older adults may be more likely to have peripheral vascular disease.
• Older adults often experience a fall in BP after eating.
• Older adults need to change position slowly and to wait after each change to avoid postural hypotension and prevent injuries.

REFERENCES

1. American Heart Association (AHA). (May 2024). How to Manage High Blood Pressure. Retrieved July 2, 2024, from https://www.heart.org/en/health-topics/high-blood-pressure/changes-you-can-make-to-manage-high-blood-pressure
2. American Heart Association (AHA). (May 2024). Home Blood Pressure Monitoring. Retrieved July 2, 2024, from https://www.heart.org/en/health-topics/high-blood-pressure/understanding-blood-pressure-readings/monitoring-your-blood-pressure-at-home#.Wuct7ExFwy9
3. American Heart Association (AHA). (May 2024). Understanding blood pressure readings. Retrieved July 2, 2024, from https://www.heart.org/en/health-topics/high-blood-pressure/understanding-blood-pressure-readings#.Wucr9UxFwy9
4. Muntner, P. and others. (2019). Measurement of blood pressure in humans: A scientific statement from the American Heart Association. Hypertension, 73(5), e35-e66. doi:10.1161/HYP.0000000000000087
5. National Heart, Lung, and Blood Institute (NHLBI). (2022). Low blood pressure. Retrieved July 2, 2024, from https://www.nhlbi.nih.gov/health-topics/hypotension
6. Pickering, T.G. and others. (2005). Recommendations for blood pressure measurement in humans and experimental animals. Part 1: Blood pressure measurement in humans: A statement for professionals from the Subcommittee of Professional and Public Education of the American Heart Association Council on High Blood Pressure Research. Hypertension, 45(1), 142-161. doi:10.1161/01.HYP.0000150859.47929.8e Retrieved July 2, 2024, from https://www.ahajournals.org/doi/full/10.1161/01.HYP.0000150859.47929.8e
7. Sheppard, J. and others. (2019). Defining the relationship between arm and leg blood pressure readings: A systematic review and meta-analysis. Journal of Hypertension, 37(4), 660-670. Retrieved July 2, 2024, from https://journals.lww.com/jhypertension/Abstract/2019/04000/Defining_the_relationship_between_arm_and_leg.2.aspx
8. Sheppard, J. and others. (2020). Measurement of blood pressure in the leg—A statement on behalf of the British and Irish Hypertension Society. Journal of Human Hypertension, 34(6), 418-419. doi:10.1038/s41371-020-0325-5

ADDITIONAL READINGS

Shimbo, D. and others. (2020). Self-measured blood pressure monitoring at home: A joint policy statement from the American Heart Association and American Medical Association. Circulation, 142(4), e42-e63. doi:10.1161/CIR.0000000000000803 Retrieved July 2, 2024, from https://www.ahajournals.org/doi/10.1161/CIR.0000000000000803

Clinical Review: Martha Beck, MA, BSN, RN, CNOR

Published: August 2024