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Non Invasive BP Measurement. Medical Physics. History of BP Measurement. 1733 Reverend Stephen Hales first to measure BP Measured the height of a column of blood after cannulating the carotid artery in a horse with a brass pipe. . History of BP Measurement.

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History of bp measurement l.jpg
History of BP Measurement

  • 1733 Reverend Stephen Hales first to measure BP

  • Measured the height of a column of blood after cannulating the carotid artery in a horse with a brass pipe.

Dr Rishi Mehra


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History of BP Measurement

  • The brass pipe was attached to a 12 inch glass tube.

  • Tube was connected to the pipe via trachea of a goose!

  • First to observe respiratory variation and pulsatile nature

  • 100 years later, Poiseuille used a mercury manometer, connected to the artery in a dog to measure BP

Dr Rishi Mehra


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History of BP Measurement

  • Both of these methods were invasive

  • First attempts at non-invasive BP measurement began in the late 1800’s

Dr Rishi Mehra


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History of BP Measurement

  • In late 1890s, Italian physician – Scipione Riva Rocci invented sphygmomanometer

  • Sphygmos = Pulse (Greek)

  • Manometer = Pressure meter

Dr Rishi Mehra


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History of BP Measurement

  • Consisted of mercury column manometer

  • Silk covering a rubber sleeve, which is filled with air

  • Squeeze bag to inflate rubber sleeve

Dr Rishi Mehra


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History of BP Measurement

  • 10 years later, a Russian surgeon – Nikolai Korotkoff discovered that sounds were present as cuff was deflated

  • Works on principle that normal blood flow is laminar, and hence silent

  • As cuff pressure drops, some blood begins to flow past compressed area of cuff

  • Blood flow is turbulent, non-laminar and audible

Dr Rishi Mehra


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History of BP Measurement

  • This method of measuring BP is called the Auscultatory method

  • Roy and Adami (1890) developed oscillometric method

  • With cuff being deflated, onset of oscillations in mercury height were noted

  • Called onset of oscillations = Systolic BP

Dr Rishi Mehra


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History of BP Measurement

  • Maximum oscillations = Diastolic (Nb Incorrect)

  • Hence all indirect BP measurement involves use of Riva-Rocci cuff, either via auscultatory measurement or via oscillometric methods.

Dr Rishi Mehra


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Automated Auscultatory Method

  • First automated systems used a microphone to replace need for manual auscultation

  • Analysis of sound produced was used to estimate SBP and DBP

  • Problems with this approach

    - External noise can lead to artefact

    - Difficulty obtaining BP where sounds may be muted eg hypotension

Dr Rishi Mehra


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Automated Auscultatory Method

  • Method used largely in 1960’s

  • Generally found to be unreliable, and often gave wide variations in BP

  • No longer used in isolation, but is incorporated in several systems in conjunction with oscillometric systems.

Dr Rishi Mehra


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Automated Oscillometric Method

  • Oscillometric method involves measuring oscillations

  • Oscillations are a result of application of cuff in order to compress artery

  • Principle of measurement involves tranducer

  • Measuring oscillations over time with decreasing cuff pressure enables estimation of BP

Dr Rishi Mehra



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Automated Oscillometric Method

  • Cuff pressure at point of maximum oscillations is taken to be MAP

  • Various methods of estimating systolic and diastolic BP from MAP

  • Auscultatory method = measure SBP and DBP and estimate MAP

  • Oscillometric method = measure MAP and estimate SBP and DBP

Dr Rishi Mehra


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Sources of error

  • Cuff size

    - Oscillations are direct result of BP cuff application - Cuff too small = overestimation of BP - Cuff too large = underestimation of BP

  • Cuff position – Bladder needs to be placed over brachial artery

Dr Rishi Mehra


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Sources of error

  • Movement

Dr Rishi Mehra


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Sources of error

  • Beat to beat variation- Oscillometric method requires reasonably stable BP during cuff deflation- Required for detecting maximum aplitude of oscillations- If BP varies due to arrhythmia, difficult to estimate BP accurately

Dr Rishi Mehra


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Sources of error

  • Beat to beat variation cont…

Dr Rishi Mehra