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Blood Pressure and Pulse
Blood Pressure and Pulse
The measurements of blood pressure and pulse are the basic tests of blood circulation.
Now let’s see that principles and methods in the following :
Blood pressure
Fig.1：The heart contraction
Blood pressure is the force that blood flow exerts on the walls of the blood vessels,
especially arteries, in the systemic circuit and it is directly related to the power of the
heart contraction.
When the ventricles contract, the blood pressure gets up to the highest value, called
systolic pressure. When the ventricles relax, the blood pressure diminishes to the
lowest value, called diastolic pressure. Blood pressure read as mmHg is measured on
the brachium by the blood pressure monitor and indicated with the systolic/diastolic
pressure formula. The following table shows the normal pressure of a person when
resting:
Adult
90~130/60~90(mmHg)
Teenager
100~110/65~75(mmHg)
If a person with the systolic pressure usually above 140/90 mmHg when resting will
be supposed to have hypertension; if below 60 mmHg, then it is low blood pressure.
Too high blood pressure will increase the load of the heart and may cause the blood
vessels to break; too low blood pressure will slow the blood flowing to decrease the
efficiency of blood transportation and further effects the normal operation of tissues
and organs. So maintaining the normal blood pressure is important for health.
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Pulse
When the ventricles contract, the blood in the left ventricle infuses to the aorta with its
wall expanding and when the atria relax, the aorta will reverberate. The pulse is the
rhythmic stretching of the arteries caused by the powerful contractions of the
ventricles during systole, it is strongest proximally to the heart and getting weak far
away from the heart, finally disappears in the capillaries.
It is easy to find the pulse on the arteries closing to the body surface or crossing over
the bones and the solid tissues. Besides the radial artery of the wrist, we can fell the
pulse on other places of the body such as superficial temporal artery in front of the ear,
facial artery in front of the mandible masseter muscle, common carotid artery in front
of the neck, brachial artery along both sides of the biceps muscle, femoral artery of
the groin and popliteal artery behinds the knee.
Since the pulse is caused by the heartbeat, so they have the same value, about 70~90
per minute when resting, in a normal adult. If the heartbeat is over 100, called
tachycardia, if under 50, called bradycardia.
Reviewed by：Zhang, Yong-Ta、Lu, Yu-Ling professor
All rights reserved by National Taiwan Science Education Center