Blood Pressure Determination Mike Clark, M.D.

The most direct (exact) method for measuring blood pressure is to insert a catheter directly into the blood vessel lumen (arterial line, Swan-Ganz, Central Venous Pressure line).

An indirect (somewhat inexact) method of obtaining systemic blood pressure is to use a blood pressure cuff (sphygmomanometer).

Note- Blowing up the blood pressure cuff changes laminar flow to turbulent flow. Turbulent flow creates a sound that can be heard with the stethoscope.

Korotkoff Sounds the sounds that medical personnel listen for when they are taking blood pressure using a non-invasive procedure. They are named after Dr. Nikolai Korotkoff, a Russian physician who described them in 1905, when he was working at the Imperial Medical Academy in St. Petersburg Korotkoff described five sequential sounds heard while deflating the blood pressure cuff The first Korotkoff sound is the snapping sound first heard at the systolic pressure. Clear tapping, repetitive sounds for at least two consecutive beats is considered the systolic pressure. The second sounds are the murmurs heard for most of the area between the systolic and diastolic pressures. The third = A loud, crisp tapping sound. The fourth sound, at pressures within 10 mmHg above the diastolic blood pressure, were described as "thumping" and "muting". The fifth Korotkoff sound is silence as the cuff pressure drops below the diastolic blood pressure. The disappearance of sound is considered diastolic blood pressure -- two mm Hg above the last sound heard. The second and third Korotkoff sounds have no known clinical significance

Proper Use of the Sphygmomanometer to Determine Systemic Blood Pressure Step One – Select the appropriate sized blood pressure cuff. There are several different adult-sized cuffs and none of the sizes are standardized (Small, Regular, Large, Thigh). Adult for arm circumference 27-34 cm Large Adult for arm circumference 35-44 cm Adult thigh Cuff for arm circumference of45-52 cm Research is VERY clear that measuring blood pressure with a cuff bladder that is the wrong size artificially alters the blood pressure result. Too small of a cuff gives an artificially high reading and too large of a cuff gives an artificially low reading.

Step Two – Palpate for the brachial artery along the inner upper arm Step Three – Wrap the cuff smoothly and snugly around the arm, centering the bladder over the brachial artery. The lower cuff edge should be 2.5 cm (1 inch) above the antecubital space. Step Four – Determine the level of maximal inflation by rapidly inflating the cuff till you cannot feel the radial pulse. To that reading add 30 mmHg. Step Five – Deflate the cuff rapidly and steadily, then wait 10 – 30 seconds before reinflating Step Six - Insert the stethoscope ear pieces, making sure they point forward. Apply the bell head of the stethoscope lightly over the brachial artery

Step Seven – Inflate the cuff rapidly and steadily to the level of maximum inflation determined in step 4. Step Eight – Release the air so that the pressure falls at 2 to 3 mm Hg per second Step Nine – Listen for the onset of at least two consecutive beats (Korotkoff's sounds, phase 1). This is the systolic pressure. Step Ten – Listen for a muffling sound (Korotkoff phase 4) with children or the cessation of sound (phase 5) in adults. This is the diastolic pressure. Continue listening for 10 – 20 mm Hg below the last sound to confirm your reading.

Film on how to take a Blood Pressure http://www.wonderhowto.com/how-to-take-someones-blood-pressure-2095/