Blood Pressure

A few things you need to know before you take blood pressure:

1) Obtain consent and introduction.
2) Explain the procedure.
3) Note down a few things:
What the person has ate, coffee, exercise, family history, strenuous activity before coming to the doctor, medication and smoking.
4) Locate the brachial and radial pulse, strap on and get the estimate of the systolic pressure.
5) Repeat second time and get the real systolic and diastolic pressure reading. Remember to mention the Korotkoff sounds while hearing the pulses.
6) Explain to the patient what the reading is. Not that readings may vary from gender and age etc etc.

According to the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH), high blood pressure for adults is defined as:

• 140 mm Hg or greater systolic pressure
  
  and
• 90 mm Hg or greater diastolic pressure

In an update of NHLBI guidelines for hypertension in 2003, a new blood pressure category was added called prehypertension:

• 120 mm Hg – 139 mm Hg systolic pressure
  
  and
• 80 mm Hg – 89 mm Hg diastolic pressure

The new NHLBI guidelines now define normal blood pressure as follows:

• Less than 120 mm Hg systolic pressure
  
  and
• Less than 80 mm Hg diastolic pressure

The Korotkoff sounds

The Korotkoff sounds are the sounds heard through the stethoscope as the pressure cuff deflates. The sounds are first heard when the cuff pressure equals the systolic pressure, and cease to be heard once the cuff has deflated past the diastolic pressure.

It is generally accepted that there are five phases of Korotkoff sounds. Each phase is characterised by the volume and quality of sound heard. The figure below illustrates these phases. In this example, the systolic and diastolic pressures are 120mmHg and 80mmHg respectively.



Phase 1

With the pressure cuff inflated to beyond the systolic pressure, the artery is completely occluded and no blood can flow through it. Consequently, no sounds are heard above the systolic pressure. At the point where cuff pressure equals the systolic pressure, a sharp tapping sound is heard. We recall that the blood pressure oscillates between systolic and diastolic pressure. At systolic, the pressure is great enough to force the artery walls open and for blood to spurt through. As the pressure dips to diastolic, however, the artery walls bang shut again. It is the closing shut of the artery walls that results in the tapping sound.

Phase 2

This phase is characterised by a swishing sound, caused by the swirling currents in the blood as the flow through the artery increases. Sometimes, if the cuff is deflated too slowly, the sounds vanish temporarily. This happens when the blood vessels beneath the cuff become congested, and is often a sign of hypertension. The congestion eventually clears, and sounds resume. The intervening period is called the auscultatory gap.

Phase 3

In this phase, there is a resumption of crisp tapping sounds, similar to those heard in phase 1. At this stage, the increased flow of blood is pounding against the artery walls.

Phase 4

At this point, there is an abrupt muffling of sound. The blood flow is becoming less turbulent. Some medical practitioners choose to record this point as the diastolic pressure.

Phase 5

This is the point at which sounds cease to be heard all together. The blood flow has returned to normal and is now laminar. The pressure cuff is deflated entirely and removed.