M5.7 Measurement of Blood Pressure

Describe the procedure of measuring blood pressure using a manual sphygmomanometer.

1) The cuff is placed around the upper arm (roughly at the same level as the heart) so that is covers the brachial artery 2) The cuff is inflated to a pressure large enough to compress the artery until it is completely closed (greater than systolic pressure) 3) This will prevent blood flowing through the artery, and can be determined by listening for the lack of blood flow sounds with a stethoscope. 4) The cuff pressure is released slowly until it is just less than the systolic pressure 5) At this point, the blood vessel will only open at the peak systolic pressure, and the blood will flow in spurts 6) The blood flow will be turbulent, and produces a characteristic sound (K-sound) which may her heard with a stethoscope placed over the artery 7) The point at which these sounds are just heard corresponds to the systolic pressure, and this is read form the manometer 8) The cuff pressure is reduced further and the artery remains open for longer periods of the cycle but is still closed during the diastolic phase 9) K sounds can still be heard, but the periods of silence become shorter as the cuff pressure drops 10) When the cuff pressure races the diastolic pressure, the artery remains open during the whole cycle 11) The flow is still turbulent and noise, but the sound is now continuous. 12) At this point, the diastolic pressure is read from the manometer.

What is the normal blood pressure for a healthy adult?

120 mmHg systole and 80 mmHg diastole

By how much does the average blood pressure drop during the night time period?

20 mmHg

What does the sphygmomanometer consist of?

An inflatable cuff (connected to a manometer) and a small hand pump, used to inflate the cuff.

Why is it important that blood pressure be monitored over prolonged periods of time?

As one single measurement can be misleading

Why is the brachial artery easy to compress?

Because of the presence of a single bone behind it

What are the ambulatory blood pressure measurements?

Blood pressure measurements that are usually conducted over periods of days, and are useful in diagnosing hypertension.

How can older patients with hypertension be characterised by?

Elevated systolic pressures. This is mainly due to a loss in compliance of the main arteries.

What does the lowest pressure in the blood pressure cycle result from?

Minimum pressure occurs following relaxation of the heart (diastolic pressure)

What does the highest pressure in the blood pressure cycle result from?

Results from maximum contraction of the heart (systolic pressure)

What is the device used for measuring blood pressure?

Sphygmomanometer - measures arterial blood pressure by observing the effect of applying an external pressure on the circulation system.

What are the range of acceptable values for systolic and diastolic blood pressures?

Systolic - 110-130 mmHg Diastolic - 70-90 mmHg

What is the pulse pressure?

The difference between the systolic and diastolic pressures.

What does the manometer measure in a sphygmomanometer?

The pressure produced by the cuff as it is inflated.

What is an important parameter for defining abnormal blood pressure?

The pulse pressure

What is the 'White Coat Syndrome'?

Where single measurements of blood pressure can be misleading, e.g. you might be nervous going to the doctors, so your blood pressure will rise.