Blood Pressure Monitoring

Introduction

Blood pressure monitoring is one of the bread-and-butter services that we offered at a community pharmacy.

  • Hypertension is mostly defined as systolic blood pressure ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg, but definitions vary by professional organization.



Blood Pressure Monitoring


Ideally, the patient should sit quietly for 5 minutes before the BP is measured. BP should be taken at least twice on each visit, with the measurements separated by one to two minutes to allow the release of trapped blood. If the second value is more than 5 mm Hg different from the first, continued measurements should be made until a stable value is attained. The recorded value on the patient's chart should be the average of the last two measurements.

# Note: Australia Heart Foundation Guide for the diagnosis and management of hypertension in adults, 2016 suggests to take 3 measurements and average the last 2 instead. If reading vary more than 10 mm Hg systolic or 6 mm Hg diastolic, have the patient rest quietly for 5 minutes then re-measure.

Key Reminders

  • The patient should avoid caffeine and smoking for at least 2 hours before measurement.
  • Neither the patient nor the observer should talk during the rest period or during the measurement.



Cuff Size and Placement

Use of a properly sized cuff is essential.

  • If too small a cuff is used, the pressure generated by inflating the cuff may not be fully transmitted to the brachial artery; in this setting, the pressure in the cuff may be considerably higher than the intraarterial pressure, which can lead to overestimation of the systolic pressure by as much as 10 to 50 mmHg in obese patients.

Cuff placement

  • Ideally, the cuff should be placed on the bare arm or over a thin sleeve.
    • The patient's sleeve should not be rolled up, as this may act as a tourniquet, nor should the measurement be taken over a thick sleeve, as this may lead to an overestimate of the patient's BP
  • The lower end of the BP cuff should be 2 to 3 cm above the elbow bend.
  • The BP cuff should be placed with the bladder midline over the brachial artery pulsation.

On the other hand, OMRON Intelli Wrap Cuff measures accurately in any position on your upper arm. It is suitable for use on arms with a circumference of 22-42 cm.



Does Body Posture Affect Blood Pressure Measured?

In short, yes.

The blood pressure should be taken when the patient is in a seated position with the back supported and legs uncrossed.

  • SBP and DBP has been reported to be 3-10 mm Hg and 1-5 mm Hg higher respectively in the supine than the seated position.
  • Moreover, SBP and DBP may be increased by 5-15 mm Hg and 5mm Hg respectively if the back is unsupported.
  • Having legs that are crossed during BP measurement may raise SBP by 5-8 mm Hg and DBP by 3-5 mm Hg.

NOTE: For some patients, particularly older adults and diabetic patients, supine, sitting and standing BPs are useful to detect orthostatic hypotension.

The arm should be supported at level of the heart. If the arm is allowed to hang down unsupported, the measured BP will be elevated by 10 to 12 mm Hg due to the added hydrostatic pressure induced by gravity.



Further Reading

If you are you interested to read more on how to do an accurate blood pressure measurement, you may be interested in the 2 articles below:

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