Non-invasive Blood Pressure

Reviewed and revised 11th July 2014


  • non-invasive blood pressure measurement involves the application of a pressure cuff and can be performed manually (listening for Korotkoff sounds as the pressure is released
  • 0 or automatically (by the oscillometric method)


  • measurement of systemic arterial blood pressure



Automatic oscillometric method

  • apply an appropriately sized cuff to upper arm
  • push start
  • single cuff inflated above systolic and then incrementally deflated while the amplitudes of cuff pressure oscillations measured by pressure transducer
  • cuff should be near level of heart
  • cuff pressure at which the amplitudes start to increase to 25-50% of maximum = systolic
  • the point of maximum oscillation = MAP (most reliable measurement)
  • cuff pressure at which the amplitudes decrease by 80% or disappear = diastolic


Disadvantages of the oscillometric method

  • inaccurate: the 95% confidence interval for blood pressure in the normal range is +/- 15mmHg!
  • can’t be easily calibrated
  • inaccurate hypovolaemic
  • cuff small -> high BP
  • can’t be used in helicopter
  • Underestimates high blood pressures
  • Overestimates low blood pressure
  • the accuracy is even worse if dysrhythmia is present


  • arrhythmias
  • muscle tremors
  • pain, limb oedema, nerve trauma

References and Links

Journal articles

  • Axler O. Measuring mean or systolic arterial pressure in critically ill patients? Invasively or noninvasively? Does it matter? Crit Care Med. 2013 Jan;41(1):333-4. PMID: 23269136.
  • Beevers G, Lip GY, O’Brien E. ABC of hypertension. Blood pressure measurement. Part I-sphygmomanometry: factors common to all techniques. BMJ. 2001 Apr 21;322(7292):981-5. PMC1120141.
  • Beevers G, Lip GY, O’Brien E. ABC of hypertension: Blood pressure measurement. Part II-conventional sphygmomanometry: technique of auscultatory blood pressure measurement. BMJ. 2001 Apr 28;322(7293):1043-7. PMC1120188.
  • Dieterle T. Blood pressure measurement–an overview. Swiss Med Wkly. 2012 Jan 27;142:w13517. doi: 10.4414/smw.2012.13517. PMID: 22287317. [Free Full Text]
  • Fred HL. Accurate blood pressure measurements and the other arm: the doctor is ultimately responsible. Tex Heart Inst J. 2013;40(3):217-9. PMC3709227.
  • O’Brien E, Beevers G, Lip GY. ABC of hypertension. Blood pressure measurement. Part III-automated sphygmomanometry: ambulatory blood pressure measurement. BMJ. 2001 May 5;322(7294):1110-4. PMC1120240.
  • O’Brien E, Beevers G, Lip GY. ABC of hypertension: Blood pressure measurement. Part IV-automated sphygmomanometry: self blood pressure measurement. BMJ. 2001 May 12;322(7295):1167-70. PMC1120288.
  • Ogedegbe G, Pickering T. Principles and techniques of blood pressure measurement. Cardiol Clin. 2010 Nov;28(4):571-86. PMC3639494.

CCC 700 6

Critical Care


Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

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