Non-invasive Blood Pressure

Reviewed and revised 11th July 2014

OVERVIEW

• 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)

USES

• measurement of systemic arterial blood pressure

DESCRIPTION

METHOD OF USE

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

OTHER INFORMATION

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

COMPLICATIONS

• 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.