• Blood pressure (BP) is the force of the blood against the wall of any blood vessel
• The systolic BP is the pressure of the blood against the artery walls when the heart contracts (beats)
• The diastolic BP is the pressure of the blood against the artery walls between heartbeats, when the heart relaxes
• Mean arterial pressure is the average pressure during the entire cardiac cycle and integrates the area under the arterial pressure waveform

• Screening for hypertension
• Assessing a person's suitability for a sport or certain occupations
• Estimation of cardiovascular risk
• Determining for the risk of various medical procedures

• Stethoscope and manual blood pressure cuff with sphygmomanometer
• Automated oscillometric device and cuff
• Appropriate size blood pressure cuff
• Length of the inflatable bladder should be 80% (almost long enough to encircle the arm)
• Width of the inflatable bladder should be at least 40% of the circumference of the upper arm (about 12-14 cm in the average adult)
• Recommend cuff sizes based on arm circumference:
• 22-26 cm, use a small adult cuff (12x22 cm)
• 27-34 cm, use an adult cuff (16x30 cm)
• 35-44 cm, use a large adult cuff (16x36 cm)
• 45-52 cm, use an adult thigh cuff (16x42 cm)
• Errors occur when the cuff is too small (measurement is high) or too large (measurement is low)

• Direct: catheter placed directly into an artery to obtain BP measurement
  
• Most accurate method but invasive
  
• Indirect:
  
• Manual cuff and sphygmomanometer:
  
• Observer and methodology errors can occur
• Automated oscillometric device
  
• Device can be inaccurate
• Ambulatory (monitors BP during 24 hr period)

• Phase I:
• Appearance of clear tapping sounds
• Correlates with systolic blood pressure
• Phase II:
• Sounds become softer and longer
• No clinical significance
• Phase III:
• Sounds become crisper and louder
• No clinical significance
• Phase IV:
• Sounds become muffled and softer
• Correlates as alternate measure of diastolic blood pressure
• Phase V:
• Sounds disappear completely
• Correlates with diastolic blood pressure

Tips to Ensure Accurate Measurement:

• Delay BP reading if patient has smoked (transient increase in BP), consumed caffeine (increase BP), or exercised (lower BP) within the past 30 minutes
• Make sure arm is free of clothing (rolling up the sleeve can cause a tourniquet around the upper arm)
• Do not place the cuff on a limb being used for intravenous or intra-arterial infusions, any area where circulation is potentially compromised, has an arteriovenous fistulas, where lymphedema exists, the risk for lymphedema exists (e.g. lymph node dissection for treatment of breast cancer), or nonintact or injured skin
• If bilateral, use lower extremities to obtain a measurement
• Palpate the brachial artery to ensure it has a viable pulse
• Position the arm so that the brachial artery is at heart level (if below the reading will be higher, if above the reading will be lower)
• While obtaining the blood pressure, neither the patient nor the person obtaining the blood pressure should talk
• Hold the dial so it faces you directly
• Avoid slow or repetitive inflations of the cuff (produces venous congestion which can falsify readings)

Manual BP Measurement:

1. Have the patient sit (comfortable, relaxed, legs uncrossed, feet resting on the floor) for 5 minutes before obtaining measurement
2. Arm should be supported at the level of the heart and slightly flexed at the elbow
3. Place the BP cuff with the bladder midline over the brachial artery pulsation
1. The lower border of the cuff should be about 2.5 cm above the antecubital crease
4. To determine the inflation level, palpate the radial artery and rapidly inflate the cuff until the pulse disappears, read this pressure on the manometer and add 30 mmHg to it
5. Deflate the cuff and wait 15-30 seconds
6. Place the stethoscope lightly over the brachial artery
1. The Korotkoff sounds are best heard with the bell of the stethoscope since they are relatively low in pitch
2. Ensure a proper seal is obtained
7. Inflate the cuff rapidly to the predetermined inflation level (see step 4)
8. Turn the bulb's screw counterclockwise to deflate slowly at a rate of 2-3 mmHg/second
9. Note the level at which you hear the sounds of at least two consecutive beats (Korotkoff phase I). This represents the patient's systolic BP
10. Continue to deflate the cuff until the sounds become muffled and disappear (Korotkoff phase V). This represents the patient's diastolic blood pressure
1. To confirm disappearance of sound, listen as the pressure falls another 10-20 mmHg
11. Deflate the cuff rapidly
12. Read the systolic and diastolic levels to the nearest 2 mmHg
13. Record the blood pressure, arm used, the arm position, and the cuff size used
14. If repeating measurement, wait ≥ 2 minutes

Automated Device:

1. Have the patient sit (comfortable, relaxed, legs uncrossed, feet resting on the floor) for 5 minutes before obtaining measurement
2. Arm should be supported at the level of the heart
3. Place the automated oscillometric cuff on the arm
1. Ensure that the cuff is the appropriate size
4. Initiate the automated device, causing it to inflate and then deflate
5. Record the BP result
6. If repeating measurement, wait ≥ 2 minutes

• To obtain a more accurate BP, the average of at least 2 measurements should be used
  
• Blood pressure should be taken in both arms at least once due to normal variance in pressure
  
• Subsequent readings should be taken in the arm with the higher pressure

1. Bickley LS et al. Bates' Guide to Physical Examination and History Taking. 11^th ed. Philadelphia, PA: Lippincott Williams & Wilkins. 2013; 118-25.

2. Perloff D et al. Human blood pressure determination by sphygmomanometry. Circulation. Nov 1993;88(5 Pt 1):2460-70.

3. Pickering TG et al. 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. Circulation. Feb 8 2005;111(5):697-716. http://circ.ahajournals.org/content/111/5/697.full