Blood Pressure
Measurement of Blood Pressure
Blood pressure can be measured using an instrument called a sphygmomanometer.
A column of mercury is linked to an inflatable cuff which is wound around the upper arm. A stethoscope is then used to listen to the sounds of the blood in the brachial artery, at the bend of the elbow.
The sounds start at the systolic pressure:
(heart contraction => higher pressure)
and finish at the diastolic pressure:
(heart relaxation => lower pressure).
Hence blood pressure is expressed as :
"height of column of Hg at systolic pressure
"
"height of column of Hg at diastolic pressure".
Normal Blood Pressure is about |
mm Hg. |
High Blood pressure is also known as 'hypertension'.
Low blood pressure is also known as 'hypotension'.
The following table summaries key causes, effects, and symptoms of 'high' and 'low' blood pressure:
|
Causes of Condition |
Effects / Symptoms |
High Blood Pressure
|
More general contributory factors are :
|
Hypertension is symptom-less until the symptoms of its complications develop. These include :
|
Low Blood Pressure
|
Can occur following:
Other causes may include:
|
Temporary Hypotension:
Severe Hypotension:
|
See also the structure and functions of blood, blood vessels, blood clotting, the structure of the heart, the functions of the heart, and systemic circulation.