The Importance of Blood Pressure Measurement
The importance of accurate blood pressure determinations cannot be
overemphasized. To obtain accurate blood pressure readings, the user requires
1) An accurate pressure measuring instrument, 2) The correct size cuff as it
relates to the circumference of the limb and 3) Good measurement technique.
Blood pressure is a very important vital sign; if it is high it can lead to
many negative health effects including heart attack, stroke and kidney
failure. About 20% of the people in the U.S. are hypertensive; many of them do
not know it because there are no symptoms to identify it. Accurate blood
pressure readings are critically important since erroneous readings can
lead to misdiagnosis and ultimately result in treatment errors.
Accurate measurement of blood pressure relies, as it always has, on the use of
a correct size cuff, good measurement technique and an instrument of known
accuracy, dependability and reproducibility. We have been providing such
instruments since 1916.
FAQ Index
What is blood pressure?
Arterial blood pressure is the force exerted by the blood on an area of the
wall of an artery as it is pushed through the circulatory system. During the
course of the cardiac cycle, the arterial blood pressure is constantly changing
. As the heart beats, the highest pressure in this cycle (systolic blood
pressure) is recorded. Between beats, the lowest pressure (diastolic blood
pressure) is recorded. The systolic number is always stated first and the
diastolic number is listed second.
For example: 122/76 (122 over 76); systolic
= 122, diastolic = 76.
Blood pressure is determined by a number of factors including:
Cardiac output
Peripheral vascular resistance
Volume of blood in the arterial system
Viscosity (density) of the blood
Elasticity of the arterial walls
The exact contribution of each factor is not known, but peripheral resistance
and cardiac output have the greatest influence on blood pressure.
FAQ Index
How can I tell if I have high blood pressure?
The only way to find out if you have high blood pressure is to have your blood
pressure checked. Your doctor or other qualified health professional should
check your blood pressure at least once every two years. Should your blood
pressure reading be elevated, you don't necessarily have high blood pressure.
However further observation is recommended.
FAQ Index
What is hypertension?
Hypertension does not refer to being tense, nervous or hyperactive. It is
simply the medical term for high blood pressure. Because high blood pressure
usually has no symptoms, many people have high blood pressure for years without
knowing it. That's why it's so dangerous.
FAQ Index
What about low blood pressure?
Generally speaking, the lower your blood pressure reading is, the better.
However, unusually low readings should be evaluated for clinical significance.
Examples include certain nerve disorders, endocrine disorders, prolonged bed
rest decreases in blood volume due to severe bleeding (hemorrhage) or
dehydration. Usually, people with dangerously low blood pressure exhibit
symptoms such as lightheadedness or fainting.
FAQ Index
How is it measured?
Blood pressure is measured through the use of a medical instrument called a
sphygmomanometer. It is a quick, painless test. A compression cuff is wrapped
around a person's upper arm and inflated. The large artery in the arm is
compressed and the flow of blood is momentarily stopped.
As the air in the cuff is released, the person measuring the blood pressure
listens with a stethoscope. When the blood starts to pulse through the artery,
it makes a sound; sounds continue to be heard until pressure in the artery
exceeds the pressure in the cuff.
As the person listens and watches the sphygmomanometer scale, he or she records
two measurements. The systolic pressure is the pressure of the blood flow when
the heart beats (the pressure when the first sound is heard). The diastolic
pressure is the pressure between heartbeats (the pressure when the last sound
is heard). Blood pressure is measured in millimeters of mercury, which is
abbreviated mm Hg. The harder it is for blood to flow, the higher the numbers
will be.
FAQ Index
What kinds of manometers are available?
There are three types of blood pressure apparatus: the mercury-gravity
manometer, the aneroid gauge and electronic devices.
The mercury-gravity manometer consists of a calibrated glass tube with a reservoir containing mercury. The reservoir communicates with the
compression cuff through a rubber tube. When pressure is exerted by inflating
the cuff the mercury rises in the glass tube.
"Once the mercury manometer is calibrated, recalibration is unnecessary. The
mercury manometer is the most reliable recorder available for the clinical
measurement of blood pressure." (Pg. 49-50 Primer of Clinical Measurement of
Blood Pressure, BURCH and DePASQUALE, Tulane University Medical School.)
The aneroid gauge consists of a metal bellows and a watch-like movement
connected to the compression cuff. Variations of pressure within the system
cause the bellows to expand and contract. Movement of the bellows rotates a
gear that turns a pointer pivoted on bearings, across a calibrated dial.
Obviously the adjustment of the mechanical system of the aneroid gauge is more
easily disturbed than that of a mercury manometer. For this reason, the
aneroid gauge must be calibrated against a mercury manometer at regular
intervals. Since the blood pressure recorded with the aneroid gauge depends
upon the elasticity of the metal bellows, it is subject to errors inherent in
the elastic properties of metal such as 'seasoning', hysteresis and drift.
Remember, the mere fact that the pointer indicates zero on the dial of the
aneroid gauge is no guarantee of accuracy over the whole pressure range.
The electronic device operates on the extrapolation of deflections of a
transducer coupled with an algorithmic derivation of a selected oscillation.
It does not use the auscultation of Korotkoff sounds.
FAQ Index
Why is the Baumanometer®
sphygmomanometer the instrument of choice?
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