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Standard operating procedure
Ambulatory Blood Pressure No: 002D
Blood pressure (BP) measurement provides an assessment of the
overall cardiovascular status of an individual. Ambulatory blood
pressure (ABP) monitoring offers a measure of BP over prolonged
periods, incorporating many physical and psychological circumstances
experienced away from the medical environment. It provides three
different types of detail, all of which have prognostic value.
These include: blood pressure level, amplitude of diurnal variation
and short-term BP variability.
may experience some tightening of their arm and subsequent arm
discomfort as a result of this procedure.
Research nurses trained in the method are responsible for teaching
subjects how the ABP monitor operates and how their data can
be collected efficiently.
blood pressure monitor (Spacelab model 90207)
- ABP cuffs
(regular and large)
- ABP carrier
- 4AA rechargeable
batteries (2 sets)
monitor should be initialised using the computer software program,
see initialisation/downloading SOP.
the ABP monitor will be pre-programmed with time intervals for
blood pressure (BP) measurements. The time intervals will be
the same for each subject and should not be altered.
Preparation of subject
to the subject the importance of the readings and the need
for their compliance in wearing the ABP cuff and monitor.
It is important to explain to the subject that during the
readings they may feel some discomfort in their arm. It is
also vital that they complete the 24 hour activity diary.
the subject in a chair and provide them with enough information
to enable them to relax (as much as possible). Answer any
questions or queries they may have regarding the procedure.
the subject which is their dominant arm and then, due to the
inconvenience of the cuff, use the non-dominant arm. Measure
the arm circumference (upper arm, widest section) using the
tape measure and choose the correct cuff size. The appropriate
cuff size to arm circumference is illustrated in figure 1.
Gross error in blood pressure recording will arise as a result
of poor measurement and inappropriate cuffs (bladders) being
American Heart Association recommends that the width of the
bladder should be 40% of the circumference of the midpoint of
the arm and that the length should be 80% of the arm circumference.
It is therefore vital that accurate measurement is taken to
prevent error in recordings (1).
- A material
casing surrounds the bladder, this should be secured around
the non-dominant arm by the velcro fastenings. The cuff (depending
on subject size) should then encircle the arm; for some subjects
this may be several times. Position the centre of the bladder
over the brachial artery, with the rubber inflation tube running
down the inner elbow and in line with the middle finger. The
cuff displays an arrow and the wording " ART" to aid
the lower edge of the cuff so it sits 2-3cm above the pulse
point of the brachial artery. The rest of the cuff should
occupy the remaining 80% of the upper arm. It should sit comfortably
on the arm; not so tight that it impairs blood circulation
or so loose that it twists around or drops out of alignment.
- Be sure
to instruct the subject how to apply and align the cuff. This
will enable the subject to reposition the cuff at home if
it becomes misaligned.
the subject to wear the cuff for the entire 24 hour period,
if possible. However, some subjects may wish to shower/bathe
and so should be instructed, by the nurse, on how to remove
the monitor briefly. This involves removing and reapplying
the cuff, as well as pausing the recording period for the
duration of their personal hygiene requirements. Removing
the cuff should be actively discouraged in order that a more
realistic blood pressure profile can be gained.
Preparation of equipment
the monitor has been initialised using the computer ABP software
program (see initialisation/downloading SOP 003 for more detail).
the monitor has 4AA previously charged batteries installed
for each new subject. As rechargeable batteries have a pre-determined
lifespan, each time they are recharged, the event should be
recorded in the battery record book. Always carry a spare
set of batteries in case of failure.
the monitor by sliding the ON/OFF switch located on
the base of the monitor. After activation the correct time
will be displayed in the small viewfinder, this is located
opposite the ON/OFF switch.
the rubber tubing from the cuff onto the luer lock attachment
on the monitor. Place the remaining tubing comfortably around
the back of the subject's neck.
the monitor in the small outer casing pouch. Attach the pouch
to the subject's belt or use the shoulder strap (whichever
preferred by the subject) to ensure the monitor is securely
attached to the subject. The opposite side of the body to
the cuff has been suggested to be the most comfortable place
for it to sit. It can also be discretely hidden under personal
clothing. The weight of the monitor is approximately 14oz.
installing both the cuff and monitor, the recordings can commence.
Press the blue ON/OFF button next to the time display.
This activates the monitor to give the first reading and will
commence the start of the 24 hour recording. This time is
noted in the subject diary as the START time. 24 hours
later, at this time, it will be the FINISH time. The
first reading will be displayed for a few seconds in the viewfinder
instead of the time. This enables both the subject and installer
to be aware that the monitor has been applied correctly.
the subject that during monitoring the cuff arm should remain
still. Unnecessary movement will impair readings. Instruct
the subject that measurements will be taken according to the
pre-programmed time intervals. Explain the noises of the monitor
to the subject, so they are not alarmed by them during each
the subject to record their daily activities in the subject
diary. These should include times when they went to bed, took
medication, watched television and travelled to work (for
examples). The analysis of the readings can then be compared
to the activities.
- If the
monitor is unable to take a reading due to excess movement
or bathing it will repeat the process 60 seconds later. All
data is stored in the monitor memory and cannot be accessed
by the subject. Subjects wishing to know their blood pressure
results, will be provided with a blood pressure profile by
the nurse. A full report with interpretation will be provided
to each participating GP for information.
24 hours, instruct the subject to switch off the monitor using
the blue ON/OFF button. The time must be EXACTLY
the same time as the START time 24 hours previously.
· Instruct the subject to remove the cuff and monitor and
return it as soon as possible to their research centre. Their
activity diary should also be submitted with the returned
monitor. This completes the subject's part in the procedure.
the monitor to the computer ABP program and download the recordings.
Guidelines for this procedure can be followed by reading the
ABP initialisation/downloading SOP 003.
monitoring, if the subject suffers undue discomfort, instruct
them to deflate the cuff by pressing the blue ON/OFF
button. However, instruct the subject that this should only
be done in extreme discomfort. Advise the subject to first
check the cuff has not slipped or become misaligned - giving
rise to the discomfort.
- For the
most reliable results, instruct the subject to keep their
arm as still as possible during the monitor recordings.
most battery operated machines it is crucial not to get the
monitor wet, as this may damage both the ABP readings taken
and the monitor.
readings are usually a result of incorrect cuff size, malpositioning
of cuff or unnecessary movement. The likelihood of these should
the subject is given a contact number in case of any concerns
or problems with the monitor (or its return).
E.T et al (1995) ABC of Hypertension, BMJ Publishing group,
2. Pickering T.G et al (1994) Ambulatory blood pressure and
prognosis, Journal of Hypertension 12, (supp18): S29-S33.
3. Padfield P.L et al (1995) Ambulatory blood pressure monitoring:
from research to clinical practice, Journal of Human Hypertension
4. Foster C et al (1993) Ambulatory blood pressure monitoring,
Nursing times, January 6, Vol 89, No 1, 33-34.
5. O'Brien E et al (1995) State of the market, A review of ambulatory
blood pressure monitoring devices, Hypertension, Vol 26, No