Blood Pressure
Introductory Note: Knowledge of the structure and functions
of blood and other aspects of the heart and vascular
system are part of training in many therapies, such
as massage, aromatherapy, acupuncture, shiatsu, and
others. This page is intended as revision notes for
basic (first level) courses in such therapies, incl.
some ITEC Diplomas.
Measurement of Blood Pressure
Blood pressure can be measured by 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".
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Normal Blood Pressure is about
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mm Hg.
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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 both "High" and "Low" Blood Pressure:
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Causes of Condition
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Effects / Symptoms
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High Blood Pressure
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- May be of unknown cause
(essential hypertension, or hyperpiesia)
- May result from kidney disease, including narrowing
of the renal artery (renal hypertension)
- Or endocrine diseases (such as Cushing's disease
or phaeochromocytoma)
- Or disease of the arteries (such as contraction
of the aorta) - which is known as secondary,
or symptomatic hypertension.
More general contributory factors are :
- Stress, Obesity, Age, Social Class, Smoking,
Lack of exercise, Poor diet.
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- Damage to arteries & veins.
- Holes get blocked up by colesterol.
Hypertension is symptom-less until
the symptoms of its complications develop.
These include :
- Atherosclerosis
- Heart failure
- Cerebral haemorrage
- Kidney failure.
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Low Blood Pressure
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Can occur following:
- Excessive fluid loss (e.g. through diarrhoea,
burns or vomiting)
- Severe blood loss (haemorrage) from any cause.
Other causes may include:
- Myocardinal infarction
- Pulmonary embolism
- Severe infections
- Allergic reactions
- Arrhythmias
- Acute abdominal conditions (e.g. pancreatitits)
- Addisons disease
- Drugs (e.g. an overdose of the drugs used to
treat hypertension).
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Temporary Hypotension:
- Simple faint (syncope)
- Light-headed
- Sweats
- Impaired conciousness
Severe Hypotension:
- Peripheral circulatory failure (cardiogenic shock)
- Unrecordable blood pressure
- Weak pulses
- Suppression of urine production
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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.
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