Blood Pressure

Blood pressure is the pressure within a person’s blood vessels. It is produced by the combination of the pumping of the heart, and of the resistance to flow that is produced by the blood vessels.

Systolic Blood Pressure measures the pressure against a person’s arterial walls when the heart contracts and pumps blood into the arteries against the resistance created by their walls.

Diastolic Blood Pressure measures the pressure against a person’s arterial walls when the heart is resting between beats. This pressure is the force that keeps the blood flowing between heart beats.

“Normal” blood pressure is now considered to be under 120/80. Hypertension (high BP) is a BP reading of greater than 139/79. For patients with certain chronic condition, such as diabetes, heart disease or chronic kidney disease the goal for BP is 129/79 or lower.

BP can be measured with an automated device or using a BP cuff and stethoscope. The following instructions apply to both methods.

Remember: talking by the observer or the patient can increase blood pressure. Also pain, emotions, bladder distention, recent caffeine or tobacco intake or a stressful physical environment can increase blood pressure.

If the initial BP is higher that expected, wait 2-5 minutes and repeat. Record both BPs.

Blood Pressure Measurement (Modified from JNC 7)

  1. Have the patient comfortably seated, back supported, legs uncrossed, for, ideally, 3 to 5 minutes.
  1. Select the proper cuff size. The bladder of the cuff should encircle at least 80% of the arm circumference. A cuff that is too small can give falsely high readings, while a cuff that is too large falsely low readings. If in doubt, use the larger cuff.
  1. Position the patient’s arm so that it is slightly flexed at heart level and preferably resting on a table. The middle of the cuff on the upper arm should be at the level of the right atrium (midpoint of the sternum). Allowing the arm to hang down will falsely elevate blood pressure.
  1. Place the cuff snugly approximately ½ inch above the elbow on a bare arm or over one thin layer if needed for patient comfort. Be careful not to create a tourniquet effect if rolling up a sleeve.

Steps 5-10 apply when a cuff and stethoscope are used

  1. Palpate the brachial artery.
  1. As you feel the radial artery, inflate the cuff until the radial pulse disappears. Read this number on the manometer and inflate to 30 mmHg above this. Use this number for subsequent readings. This avoids the occasional error caused by an ausculatory gap.
  1. Place the stethoscope lightly over the brachial artery just above the elbow crease.
  1. Deflate the cuff slowly at a rate of 2 to 3 mmHg per second.
  1. The systolic (top) pressure is equal to the pressure when the first sound is heard.
  1. The pulse continues to be heard, becomes muffled and then the sound disappears. This is the diastolic (bottom) pressure. To confirm the disappearance of sounds, listen as the pressure falls another 10 to 20 mmHg. Then deflate rapidly to zero.