The next step in arterial pulse assessment is to determine this patient's blood pressure. Let us now determine that blood pressure, placing the diaphragm of the stethoscope over the brachial area.
Our patient's blood pressure is 120/70 mmHg, that is, the blood pressure is normal.
Technique
Another element of arterial pulse assessment is blood pressure determination. The brachial artery is first identified by palpation. Then, we inflate the blood pressure cuff until the brachial pulse disappears. The next step is to place the diaphragm of the stethoscope over the brachial artery. We then slowly inflate the cuff... Exceeding that point where the pulse had been obliterated, and then, as we deflate the cuff, we hear the Korotkoff sounds. The very first Korotkoff sound identifies the systolic blood pressure and, as we come down and further deflate the cuff... The very last Korotkoff sound identifies the diastolic pressure.
Physiology
The blood pressure is a force exerted against the arterial wall. The physiologic explanation of the systolic pressure relates to the force exerted when the ventricles contract and it is largely the result of stroke volume and arterial vessel elasticity or stiffness.
The diastolic pressure is the force exerted when the heart is filling or relaxed, and is primarily due to peripheral vascular resistance.
Korotkoff sounds are sounds originating in the arterial vessel and are related to the turbulence of blood flow produced by partially occluding the artery with the blood pressure cuff.
Size and fit
To obtain an accurate systolic pressure, the cuff should be inflated to about 30 mm of Hg above the patient's systolic pressure, as determined by palpating the radial or brachial artery while simultaneously inflating the cuff.
Cuff size and fit must be appropriate.
Normal BP
In the adult, a resting blood pressure of less than 120/80 mm of Hg is within normal limits.
Measurements should be made with the patient at rest and without emotional stress. In general, as long as the patient is asymptomatic, the lower the blood pressure, the better.