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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 30, No 2, March/April 2019
AFRICA
123
diastolic blood pressures by processing the oscillometric pulses
generated from the arterial wall.
The cuff may be applied at different sites of the body including
arm, wrist and finger. Clinicians and investigators should note
that the blood pressure will change the more distal and inferior
to the heart the cuff is applied. Importantly, automated blood
pressure devices may be used within and outside the health
facility such as at home, and examples are listed in Table 2.
Oscillotonometry: this functions by reconstructing
the brachial blood pressure waveform from a finger blood
pressure waveform.
92
Finapres
61
(FINger Arterial PRESure)
and Finometer
92
are examples of finger devices that function as
continuous non-invasive blood pressure monitors.
93
Portapres
is a non-invasive ambulatory finger blood pressure device.
94
Continuous non-invasive blood pressure monitoring is finding
use in pregnancy, such as inmonitoring fluctuating blood pressure
during caesarean delivery under subarachnoid blockade.
95
Semi-automated device: the Microlife 3AS1-2 is a deflationary
semi-automated cheap and accurate device that has been
validated and approved for use in pregnancy (Table 2), especially
in LMIC.
84
This device was validated in a research project called
CRADLE (Community blood pressure monitoring in Rural
Africa and Asia: Detection of underLying pre-Eclampsia).
36
During its use, the cuff needs to be applied on the arm and
inflated manually above the systolic blood pressure. The device
is semi-automated partly because it uses batteries (two AAA
batteries) and the blood pressure displays automatically during
manual deflation of the cuff but requires no auscultation.
96
Another example of a semi-automatic arm-type blood pressure
device is UA-704 (A&D Company, Ltd, Tokyo, Japan).
97
Home blood pressure monitor: this has a role in the
management of hypertension as long as the device has been
checked for accuracy.
98
It has great value in the diagnosis
of white-coat and masked hypertension when the use of an
ambulatory blood pressure monitor is not practicable. The
reading may alert the user to seek medical attention for further
evaluation and adjustment of the dose of antihypertensive
therapy.
99
It also has the potential to reduce the number of
patient visits to health facilities.
100
A comprehensive assessment of blood pressure with a home
device is obtained by measuring the blood pressure on two
separate occasions in the morning hours and twice at different
times in the evening for at least three days
101
but preferably five
Table 1.Techniques of auscultatory and automated blood pressure (BP) measurement
Initial steps for both auscultatory and automated methods
1. If the equipment for BP measurements are available, the first step of the procedure is patient preparation. Discuss the reason and the steps involved in BP measure-
ment with the patient and/or her guardian. May not be applicable in some emergency situations.
2. Obtain permission to measure BP.
3. Examine the radial or brachial pulse and determine the rate and regularity.
68
Automated devices may be inaccurate if the pulse is irregular.
4. Assemble the equipment for BP measurement, if not yet done. A validated device with a valid calibration status is required. Auscultatory method requires a func-
tional stethoscope.
5. Ideally, the woman should rest for > 5 minutes
69
seated quietly with her shoulders supported comfortably on a backrest of a chair/seat.
70,71
Left lateral decubitus
position may be used if patient is unable to sit.
72
6. Expose the arm and determine its circumference to select appropriate cuff. The cuff should be 1.5 times the mid-upper arm circumference
70
and the bladder encir-
cles 80% of arm.
69
BP should be measured on both arms during the first visit. The arm where the BP is highest should be used for the subsequent measurement,
70,71,73
especially if the systolic BP difference is > 20 mmHg.
74
The left arm should be used for measurement if BP of both arms cannot be assessed initially. Cuff size of 15
cm should be used if the arm circumference is > 33 cm.
73
7. Wrap the bare arm with the cuff and ensure that the bladder is centred over the brachial artery.
71
The patient’s arm should be outstretched and the mid-width of
the cuff should be at same horizontal plane with the right atrium (i.e. at the level of mid-length of the sternum).
69
The patient should not cross her legs.
71
The cuff
should be placed to expose the cubital fossa and aid auscultation of the brachial artery.
Steps specific to auscultatory methods only
8. Palpate the radial artery, keep doing so and inflate the cuff to a pressure where the radial artery pulsation disappears. Then deflate the cuff completely. This step
prevents missing an auscultatory gap.
71
The pressure level where the radial artery pulsation disappears is an estimate of the systolic BP.
9. Inflate the cuff up to 20–30 mmHg above the pressure level at which the radial artery pulsation disappeared. Then deflate the pressure at a rate of 2 mmHg/sec
while auscultating the brachial artery at the cubital fossa using a functional stethoscope.
75
The pressure at which the 1st sound (Korotkoff sound) is heard repre-
sents the systolic BP and the disappearance of the sound (Korotkoff V) denotes the diastolic BP.
76
If the Korotkoff sound does not disappear, the pressure at which
the sound muffles (Korotkoff IV) will denote diastolic BP. Auscultation of the artery is not required when using an automated BP device.
Further steps for both auscultatory and automated methods
10. For auscultatory device, repeat step 9 above twice at intervals of 1–2 minutes
69
apart to obtain 2nd and 3rd BP readings. Discard the 1st reading as this is a range-
finding measurement.
6
Determine the average of the 2nd and 3rd readings to obtain the BP of the patient.
6,71
For automated device, the average of a total of two
measurements (1st and 2nd) should be regarded as the BP value.
6
The National Institute of Clinical Excellence recommends: if the 1st BP is > 140/90 mmHg, take 2nd measurement. If the difference between the 1st and 2nd readings is
substantial, take 3rd measurement. The lowest reading should be regarded as the BP.
68
11. Re-check the BP in the next 15 minutes if severe hypertension (BP > 160/110 mmHg) is diagnosed.
77
Repeating BP measurement assists to exclude the effect of
anxiety.
12. Explain the BP reading to patient/guardian and institute further care.
Table 2. Examples of automated blood pressure devices
validated in pregnancy and pre-eclampsia
Home devices
• Omron MIT.
80
• Omron M7 (HEM-780-E).
80
Clinic devices
• Omron MIT Elite (HEM-7300-WE).
82
• Microlife 3AS1-2 (semi-automatic device).
83,84
• Microlife WatchBP Home (BP3MX1-1).
85
• Omron Evolv (HEM-7600T-E). Validated in pregnancy.
86
• Omron M3 Comfort (HEM-7134-E). Validated in pregnancy.
86
• A&D UM-101.
59
• Omron HEM907.
59
• Dinamap ProCare 400.
87
• Nissei DS-400.
88
Ambulatory devices
• BP lab.
89,90
• Welch Allyn QuietTrak.
91