British Hypertension Society - blood pressure measurement

Last edited 09/2019 and last reviewed 08/2021

General criteria to be observed in assessing blood pressure by standard mercury or semi-automated device

• use a properly calibrated, maintained, and validated device
• measure sitting blood pressure routinely:
  • standing blood pressure should be recorded at least at the initial estimation in elderly or diabetic patients
• remove tight clothing, support arm at heart level, ensure arm relaxed and avoid talking during the measurement procedure
• use cuff of appropriate size (bladder width x length )
  • small adult/child - 12x18 cm - if arm circumference < 23cm
  • standard adult - 12 x 26 cm if arm circumference > 23 and < 33 cm
  • large adult - 12 x 40 cm if arm circumference > 33 and < 50 cm
  • adult thigh cuff - 20 x 42 cm - if arm circumference > 50 and < 53 cm
• lower mercury column slowly (2 mm per second)
• read blood pressure to the nearest 2 mm Hg
• measure diastolic blood pressure as disappearance of sounds (phase V)
• take the mean of at least two readings, more recordings are needed if marked differences between initial measurements are found
• do not treat on the basis of an isolated reading
• patient seated
• use conventional mercury manometer with an appropriate bladder size
• diastolic reading taken at disappearance of sound - phase V
• record to nearest 2 mm Hg
• at least two BP measures at each visit
• at least four separate visits to determine BP threshold - but with severe hypertension, delaying further management may not be justified

Notes:

• all adults should have blood pressure measured routinely at least every five years until the age of 80 years
• patients with "high normal" systolic blood pressure (130-139 mm Hg) or diastolic blood pressure (85-89 mm Hg) and patients who have had high blood pressure readings at any time previously should have their blood pressure measured annually
• seated blood pressure recordings are generally sufficient, but standing blood pressure should be measured in elderly or diabetic patients to exclude notable orthostatic hypotension. The average of two readings at each of a number of visits (depending on severity) should be used to guide the decision to treat

Reference:

1. Williams B, Poulter NR, Brown MJ, Davis M, McInnes GT, Potter JF, et al. Guidelines for management of hypertension: report of the fourth working party of the British Hypertension Society, 2004—BHS IV. J Hum Hypertens 2004;18: 139-85