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May.27.2021

Blood Pressure: Auscultation of Lower Extremity (Ambulatory) - CE

ALERT

If unable to palpate an artery because of a weak pulse, use an ultrasonic stethoscope (Figure 1)Figure 1.

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

OVERVIEW

BP is the force exerted by blood against the vessel walls. During a normal cardiac cycle, BP reaches a peak, 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 the 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 2)Figure 2. BP is recorded with the systolic reading (first Korotkoff sound) before the diastolic reading (beginning of the fifth Korotkoff sound). 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.

Cuff size should be proportionate to the extremity circumference (Table 1)Table 1. Most adults require a large adult cuff. An improper-size cuff produces an inaccurate BP measurement (Table 2)Table 2. Studies show that 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.undefined#ref1">1

When measuring BP in the upper arm is not possible—for example, when the available BP cuffs do not fit the upper arm properly—BP may be measured in the forearm. To obtain the most accurate reading, a proper size BP cuff for the forearm should be used; it typically has a smaller circumference than the upper arm. BP measurements in the forearm and upper arm are not interchangeable. Systolic blood pressure readings tend to be higher in more distal arteries, such as those in the forearm, and diastolic blood pressure readings tend to be lower in the more distal arteries.7,8 The thigh or calf can be used if measurement of the upper arms and forearms is not possible.1

EDUCATION

  • Provide developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, and overall neurologic and psychosocial state.
  • Explain the equipment and the procedure to the patient.
  • Instruct the patient about ambulatory BP threshold guidelines. In adults, normal BP is less than 120/80 mm Hg2,5 (Table 3)Table 3.
  • Educate the patient about the risk factors for hypertension.
    • Family history of hypertension, premature heart disease, lipidemia, or renal disease
    • Obesity
    • Cigarette smoking
    • Heavy alcohol consumption
    • High blood cholesterol and triglyceride levels
    • Prolonged stress from psychosocial and environmental factors
    • Sedentary lifestyle
  • Educate the patient and family regarding the primary strategies for preventing hypertension.3
    • Managing weight
    • Limiting sodium and saturated fat in the diet
    • Taking medications as prescribed
    • Maintaining adequate intake of dietary potassium and calcium
    • Engaging in daily exercise
    • Limiting alcohol intake
    • Avoiding tobacco products
  • Teach the patient the signs and symptoms of high BP (e.g., shortness of breath, severe headache, severe anxiety, pulsations in the neck or head) and provide instructions on when to seek additional care.
  • Instruct the patient to get adequate rest before BP measurements, which should be performed at the same time each day using the same leg with the patient in the same position, either prone or supine.
  • Explain to the patient the necessity of remaining still and quiet during the procedure.
  • Encourage questions and answer them as they arise.

PROCEDURE

  1. Perform hand hygiene. Don appropriate personal protective equipment (PPE) based on the patient’s need for isolation precautions or risk of exposure to bodily fluids.
  2. Introduce yourself to the patient.
  3. Verify the correct patient using two identifiers.
  4. Explain the procedure and ensure that the patient agrees to treatment.
  5. Ensure that evaluation findings are communicated to the clinical team leader per the organization’s practice.
  6. Review the patient’s record for a history of hypertension, cardiovascular disease, renal disease, diabetes, and other factors that may influence BP (e.g., weight, smoking, medications).
  7. Evaluate the patient for signs and symptoms of BP alterations.
    1. Determine if the patient is at risk for high BP if the patient is experiencing these signs and symptoms:
      1. Headache (usually occipital)
      2. Facial flushing
      3. Nosebleed
      4. Fatigue
    2. Determine if the patient is at risk for low BP if the patient is experiencing these signs and symptoms:
      1. Dizziness
      2. Mental confusion
      3. Restlessness
      4. Pale, dusky, or cyanotic skin and mucous membranes
      5. Cool, mottled skin over the extremities
  8. Determine the best site for BP measurement. Avoid applying the cuff to the patient’s leg in these situations:
    1. The leg has been traumatized.
    2. The leg has known infections or medical conditions (e.g., those causing vasoconstriction or a tumor pressing on the vascular supply).
    3. The leg has a cast or bulky bandage.
  9. If available, review the previous baseline BP and measurement site from the patient’s record.
  10. Determine the appropriateness of using an electronic BP measurement (Box 1)Box 1.
  11. Ensure that the patient has not exercised, ingested caffeine, or smoked for 30 minutes before BP measurement.4 Ensure that the patient does not have to void.
  12. Rationale: The urge to void can significantly increase BP. 6
  13. Ensure that the room is warm.
  14. Rationale: Exposure to cold can significantly increase systolic BP. 6
  15. Measure the patient’s thigh circumference and select the appropriate-size cuff (Table 1)Table 1.
  16. Rationale: An improper-size cuff produces inaccurate BP measurements. Studies show that using a cuff that is too narrow results in an overestimation of BP and using a cuff that is too wide results in an underestimate of BP. 1
  17. Inform the patient that BP will be taken and that the cuff will squeeze the leg.

Auscultation Method

  1. Perform hand hygiene. Don additional appropriate personal protective equipment (PPE) based on the patient’s need for isolation precautions or risk of exposure to bodily fluids.
  2. Verify the correct patient using two identifiers.
  3. Explain the procedure and ensure that the patient agrees to treatment.
  4. Ensure that evaluation findings are communicated to the clinical team leader per the organization’s practice.
  5. Assist the patient to a prone position. If unable to assume a prone position, assist the patient into a supine position with the knee slightly flexed. Ask the patient not to cross the legs.
  6. Rationale: The prone position provides the best access to the popliteal artery. Leg crossing can falsely increase systolic and diastolic BP.
  7. Expose the patient’s leg fully by removing constricting clothing. Do not place the BP cuff over clothing.
  8. Rationale: Placing the cuff over clothing may affect the BP measurement.
  9. 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.1
      3. Apply the cuff by centering the arrows marked on the cuff over the popliteal artery so that the lower edge of the cuff is 2 to 3 cm (about 1 inch) above the popliteal fossa to allow room for placement of the stethoscope.1 If the cuff has no center arrows, estimate the center of the bladder and place it over the artery (Figure 3)Figure 3.
      4. Rationale: Positioning the cuff bladder directly over the popliteal artery ensures that proper pressure is applied during inflation.
      5. Wrap the fully deflated cuff evenly and snugly around the patient’s thigh.
      6. Rationale: A loose-fitting cuff can cause an artificially high reading.
    2. Calf
      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.1
      3. Apply the cuff so that the lower edge is 2 to 3 cm (about 1 inch) above the malleoli.1
      4. Wrap the fully deflated cuff evenly and snugly around the patient’s calf.
      5. Rationale: A loose-fitting cuff can cause an artificially high reading.
  10. Position the manometer vertically at eye level.
  11. Rationale: Looking up or down at the scale can result in incorrect readings.
  12. Ask the patient not to speak while BP is being measured.
  13. Place the stethoscope earpieces in the ears and make sure that sounds are clear, not muffled.
  14. Locate the popliteal artery for thigh BP, or the dorsalis pedis or posterior tibial artery for calf BP, and place the diaphragm of the stethoscope over it below the lower edge of the cuff.
    1. Rationale: Using the bell of the stethoscope may cause an inaccurate measurement. 6
    2. Do not allow the chest piece to touch the cuff or clothing.
    3. Do not place the diaphragm under the cuff.6
    4. Do not place excessive pressure on the stethoscope head.6
    5. If unable to palpate the artery because of a weakened pulse, use an ultrasonic stethoscope (Figure 1)Figure 1.
    6. Rationale: Proper stethoscope placement ensures the best sound reception. An improperly positioned stethoscope can cause muffled sounds that can result in an artificially low systolic and an artificially high diastolic reading. Use of the bell and excessive pressure on the diaphragm of the stethoscope can lead to inaccurate BP measurements. 6
  15. 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.
  16. Rationale: Closing the valve prevents air leak during inflation. Rapid cuff inflation ensures accurate measurement of systolic pressure.
  17. 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.6
  18. Rationale: Too rapid or too slow a decline in the mercury level can cause an inaccurate measurement.
  19. Observe the point on the manometer at which the first Korotkoff sound is heard, indicating the systolic BP. The sound slowly increases in intensity.
  20. Rationale: The first Korotkoff sound is a snapping sound. This sound for at least two consecutive heartbeats reflects the systolic BP.
  21. Continue to deflate the cuff gradually; observe the point on the manometer at which all Korotkoff sounds disappear, indicating the diastolic BP.
  22. 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. 6 The fourth Korotkoff sound involves distinct muffling of sounds and indicates diastolic pressure in children. 9
  23. When the sounds disappear, quickly deflate the cuff completely.
  24. Remove the cuff from the patient’s leg unless a repeat measurement is needed.
  25. Rationale: Continuous cuff inflation causes arterial occlusion, resulting in numbness and tingling of the patient’s leg.
  26. If this is the patient’s first BP evaluation, repeat the procedure on the other leg.
  27. Rationale: Comparison of BP in both legs helps detect cardiovascular, neurologic, and musculoskeletal abnormalities. A normal difference of up to 10 mm Hg may exist between legs. 1
  28. Assist the patient with resuming a comfortable position and cover the leg if previously clothed. Inform the patient of the BP reading, as appropriate.
  29. Clean the BP cuff per the manufacturer’s instructions and the organization’s practice. Clean the earpieces and diaphragm of the stethoscope per the organization’s practice.
  30. Return the equipment to its assigned storage space.
  31. Remove any PPE and perform hand hygiene.
  32. Document the procedure in the patient’s record.

Electronic Method

  1. Perform hand hygiene. Don additional appropriate PPE based on the patient’s need for isolation precautions or risk of exposure to bodily fluids.
  2. Verify the correct patient using two identifiers.
  3. Explain the procedure and ensure that the patient agrees to treatment.
  4. Ensure that evaluation findings are communicated to the clinical team leader per the organization’s practice.
  5. Assist the patient to a prone position. If unable to assume a prone position, assist the patient into a supine position with the knee slightly flexed. Ask the patient not to cross the legs.
  6. Rationale: The prone position provides the best access to the popliteal artery. Leg crossing can artificially increase BP.
  7. Plug in the device and place it near the patient’s leg and then choose an appropriate-size cuff (Table 1)Table 1. Ensure that the BP cuff is appropriate for the electronic device per the manufacturer’s instructions.
  8. Prepare the BP cuff by manually squeezing all the air out of it and connecting it to the connector hose.
  9. Expose the patient’s leg fully by removing constricting clothing. Do not place the BP cuff over clothing.
  10. Rationale: Placing the cuff over clothing may affect the BP measurement.
  11. Apply the BP cuff. Do not place the cuff over a bony prominence, superficial nerve, or joint.1
    1. Thigh
      1. Palpate the popliteal artery for a pulse.
      2. Position the cuff over the lower third of the patient’s thigh.1
      3. Apply the cuff by centering the arrows marked on the cuff over the popliteal artery so that the lower edge of the cuff is 2 to 3 cm (about 1 inch) above the popliteal fossa.1 If the cuff has no center arrows, estimate the center of the bladder and place it over the artery (Figure 3)Figure 3.
      4. Rationale: Positioning the cuff bladder directly over the popliteal artery ensures that proper pressure is applied during inflation.
      5. Wrap the fully deflated cuff evenly and snugly around the patient’s thigh.
      6. Rationale: A loose-fitting cuff can cause an artificially high reading.
    2. Calf
      1. Position the cuff over the lower half of the patient’s calf.1
      2. Apply the cuff so that the lower edge is 2 to 3 cm (about 1 inch) above the malleoli.1
      3. Wrap the fully deflated cuff evenly and snugly around the patient’s calf.
      4. Rationale: A loose-fitting cuff causes false-high readings ( Table 2)Table 2.
  12. Ask the patient not to speak while BP is being measured.
  13. Verify that the connector hose between the cuff and the machine is not kinked.
  14. Set the frequency control for automatic or manual and then press the start button following the manufacturer’s instructions.
  15. When the deflation is complete, observe the digital display, which provides the most recent values. Displays vary among different types of BP monitors.
  16. Obtain additional readings by pressing the start button rather than the cancel button.
  17. Rationale: Pressing the cancel button immediately deflates the cuff.
  18. If frequent BP measurements are required, leave the cuff in place. Set the frequency of BP measurements and the upper and lower alarm limits for systolic, diastolic, and mean BP readings.
    1. Remove the cuff at regular intervals to inspect the underlying skin integrity.
    2. Alternate BP sites, if possible.
    3. A patient with abnormal bleeding tendencies is at risk for microvascular rupture from repeated inflations.
  19. Remove the cuff from the patient’s leg unless a repeat measurement is needed.
  20. Rationale: Continuous cuff inflation causes arterial occlusion, resulting in numbness and tingling of the patient’s leg.
  21. If this is the patient’s first BP evaluation, repeat the procedure on the other leg.
  22. Rationale: Comparing BP in both legs helps detect circulatory problems.
  23. Assist the patient with resuming a comfortable position and cover the leg if previously clothed. Inform the patient of the BP reading, as appropriate.
  24. Clean the BP cuff and the electronic device per the manufacturer’s instructions and the organization’s practice.
  25. Return the equipment to its assigned storage space.
  26. Remove any PPE and perform hand hygiene.
  27. Document the procedure in the patient’s record.

EXPECTED OUTCOMES

  • BP is within acceptable range for the patient’s age and body size.
  • Patient tolerates procedure.
  • Left leg and right leg BP readings are within acceptable ranges of each other.

UNEXPECTED OUTCOMES

  • BP is above acceptable range for the patient’s age and body size.
  • BP is below acceptable range or insufficient for adequate perfusion and oxygenation of tissues for the patient’s age and body size.
  • BP reading cannot be obtained.
  • Patient experiences orthostatic hypotension.
  • A significant difference exists between left leg and right leg BP readings.

DOCUMENTATION

  • BP measurement
  • Method
  • Site used and patient’s position
  • BP measurement after administration of specific therapies
  • Signs and symptoms of BP alterations
  • Abnormal findings
  • Unexpected outcomes and related interventions
  • Education
  • Evaluation findings communicated to the clinical team leader per the organization’s practice

PEDIATRIC CONSIDERATIONS

  • Thigh BP measurement is uncomfortable for children. The right arm is preferred for BP measurement in children.9
  • BP measurement may frighten children. The child should be prepared for the squeezing feeling of the inflated BP cuff by comparing the sensation to an elastic band on a finger or a tight hug.
  • The child’s BP should be measured before performing anxiety-producing tests or procedures.
  • A child’s or adolescent’s awareness of body size and age should be considered during the BP measurement.
    • Heavier and taller children have a higher BP than smaller children of the same age.
    • During adolescence, BP continues to vary according to body size.
  • An acceptable chart for expected ranges that is based on age, height, and weight should be used.
  • Korotkoff sounds are difficult to hear in children because of their low frequency and amplitude. Using a pediatric stethoscope is helpful.
  • Though the beginning of the fifth Korotkoff sound indicates diastolic pressure in adults, the fourth Korotkoff (distinct muffling) indicates diastolic pressure in children.

OLDER ADULT CONSIDERATIONS

  • Older adults’ skin is more fragile and susceptible to damage from cuff pressure when BP measurements are frequent. More frequent evaluations 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.
  • In most cases, older adults experience a fall in BP after eating.
  • Older adults should be instructed to change position slowly and to wait after each change to avoid postural hypotension and prevent injuries.

REFERENCES

  1. American Association of Critical-Care Nurses (AACN). (2016). AACN practice alert: Obtaining accurate noninvasive blood pressure measurements in adults. Critical Care Nurse, 36(3), e12-e16. doi:10.4037/ccn2016590 (Level VII)
  2. American Heart Association (AHA). (2017). Changes you can make to manage high blood pressure. Retrieved April 8, 2021, from https://www.heart.org/en/health-topics/high-blood-pressure/changes-you-can-make-to-manage-high-blood-pressure
  3. American Heart Association (AHA). (2017). Monitoring your blood pressure at home. Retrieved April 8, 2021, from https://www.heart.org/en/health-topics/high-blood-pressure/understanding-blood-pressure-readings/monitoring-your-blood-pressure-at-home#.Wuct7ExFwy9 (Level VII)
  4. American Heart Association (AHA). (2017). The facts about high blood pressure. Retrieved April 8, 2021, from https://www.heart.org/en/health-topics/high-blood-pressure/the-facts-about-high-blood-pressure (Level VII)
  5. American Heart Association (AHA). (2021). Understanding blood pressure readings. Retrieved April 8, 2021, from https://www.heart.org/en/health-topics/high-blood-pressure/understanding-blood-pressure-readings#.Wucr9UxFwy9 (Level VII)
  6. Kallioinen, N. and others. (2017). Sources of inaccuracy in the measurement of adult patients’ resting blood pressure in clinical settings: A systematic review. Journal of Hypertension, 35(3), 421-441. doi:10.1097/HJH.0000000000001197 (Level I)
  7. 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 (Level VII)
  8. Pickering, T. 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), 142-167. (classic reference)* Retrieved April 8, 2021, from https://www.ahajournals.org/doi/full/10.1161/01.HYP.0000150859.47929.8e (Level VII)
  9. Schroeder, M.L. and others. (2019). Chapter 27: The child with cardiovascular dysfunction. In M.J. Hockenberry, D. Wilson, C.C. Rodgers (Eds.), Wong’s nursing care of infants and children (11th ed., pp. 958-1019). St. Louis: Elsevier.

ADDITIONAL READINGS

American Heart Association (AHA). (2017). What is high blood pressure? Retrieved April 8, 2021, from https://www.heart.org/en/health-topics/high-blood-pressure/the-facts-about-high-blood-pressure/what-is-high-blood-pressure (Level VII)

*In these skills, a “classic” reference is a widely cited, standard work of established excellence that significantly affects current practice and may also represent the foundational research for practice.

Elsevier Skills Levels of Evidence

  • Level I - Systematic review of all relevant randomized controlled trials
  • Level II - At least one well-designed randomized controlled trial
  • Level III - Well-designed controlled trials without randomization
  • Level IV - Well-designed case-controlled or cohort studies
  • Level V - Descriptive or qualitative studies
  • Level VI - Single descriptive or qualitative study
  • Level VII - Authority opinion or expert committee reports
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