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How to measure blood pressure using digital monitors

Blood pressure is the pressure exerted by circulating blood

upon the walls of blood vessels.

"Systolic pressure" is the blood pressure when the heart contracts.

"Diastolic pressure" is the pressure when the heart relaxes.


Hypertension (or high blood pressure) is a chronic disease.

An adult is said to have hypertension if his systolic blood pressure (SBP)

is persistently above or equal to 140 mmHg,

or if his diastolic blood pressure (DBP)

is persistently above or equal to 90 mmHg.


Generally, an adult should keep his SBP

below 120 and DBP below 80 mmHg.


Checking blood pressure regularly and accurately

helps early detection and management of hypertension.

Adults 18 years or above should have their blood pressure

checked at least once every two years.


The frequency of blood pressure monitoring

may need to be adjusted depending on the

individual's blood pressure level, age,

overall cardiovascular risk profile, and doctor's advice.


Easy-to-use digital blood pressure monitors are now available.

Users can measure blood pressure themselves

for self-monitoring the blood pressure.


Pay attention to the way the blood pressure is measured.

If it is wrong, for example, a cuff placed in improper positions,

the readings may be inaccurate and lead to inappropriate treatment.


Here are some tips on choosing an appropriate blood pressure monitor

and getting accurate measurements:


First, how to choose an appropriate blood pressure monitor?


The common digital monitors can measure blood pressure

on the upper arm or the wrist.

Upper arm devices are preferred as they are more accurate.


Devices that measure blood pressure at the finger

are not recommended.


Blood pressure cuffs come in different sizes.

Make sure the cuff size fits your arm.

Using an incorrect cuff may give inaccurate results.


The width of the cuff should cover two-thirds of the upper arm.

The cuff should be long enough to encircle the whole arm.

People with brawnier arm or who are overweight may need bigger cuffs.


You can consult your doctor or the supplier on the appropriate type of blood pressure monitor and cuff size.


An accurate blood pressure monitor is the key to accurate readings:


Choose blood pressure monitors that are clinically validated.

Read the manual carefully before operating the device,

and follow the manufacturer's instructions.


The blood pressure monitor

should have regular maintenance and calibration.


Blood pressure readings taken at home may differ

from those taken at your doctor's office.

If you have any doubts, bring your blood pressure monitor along

to your doctor's appointment.

Your doctor can help validate your blood pressure readings.


For accurate blood pressure measurement,

consider the time and place to measure blood pressure,

and your body conditions:


Measure blood pressure at around the same time each day.

Measure blood pressure in a quiet environment.

Do not measure blood pressure when you feel unwell,

cold, anxious, stressed, in pain, or have a full bladder.


Before taking measurements:


Do not exercise, smoke or consume foods

or drinks containing caffeine (such as tea or coffee)

at least 30 minutes before measurement.

Wear loose-fitting and comfortable clothes.

Rest and relax for 5 minutes without any distractions

such as watching television.


Measuring blood pressure:


Choose a stable table and chair of appropriate height.

Sit comfortably and relaxed with your back supported.

Make sure your arm is supported on a tabletop

at an even level with your heart.


Keep your feet on the floor and do not cross the legs.


Roll up the sleeve to expose your upper arm and wrap the cuff around it.


The lower border of the cuff should be 2 cm above the pit of elbow,

which is approximately two finger-breadths.

Make sure the tubing is placed at the centre of your arm

facing the front and that the sensor is correctly placed.

Pull the end of the cuff so that it is wrapped evenly

and firmly around your arm.


Check that the tightness of the cuff is appropriate:

you should be able to just slip two fingertips beneath the cuff,

near its edge at the top end;

when the cuff inflates it should not cause any painful sensation.


Before starting, wait and relax for a few moments.

Press the "start" button.

During measurement, stay relaxed, keeping still and quiet.


The cuff will inflate, then slowly deflate.

When the measurement is complete, readings of your SBP,

DBP and pulse rate will be displayed on the digital panel.


Record the reading of the first measurement.


After completing the first measurement, release the cuff completely.

Obtain another reading of blood pressure after resting.

Allow an interval of at least 1 minute between the two measurements.


Recording the blood pressure readings:


Take the average value of the two readings.

If the two readings differ by more than 5 mmHg,

one additional reading should be obtained before taking the average.


Record the dates and readings into a record book

for ongoing monitoring of blood pressure.


Bring your blood pressure readings at your next follow-up appointment

for your doctor's reference.


Consult a doctor or a nurse if you have any concerns.


Further Information:


Centre for Health Protection website's World Health Day 2013 Page

www.chp.gov.hk


Primary Care Office website

www.pco.gov.hk


Central Health Education Unit website

www.cheu.gov.hk

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