Oscillometric blood pressure measurement

[Ref: KB Primary course May 2005]

Originally introduced in DINAMAP monitors.
* "Device for Indirect Noninvasive Automatic Mean Arterial Pressure" measurement

DINAMAP is only one example of oscillometric manometer.

Principle

• When cuff pressure > systolic BP
  --> no fluctuations in cuff pressure
• When cuff pressure = SBP
  --> small pressure fluctuations
• When cuff pressure falls
  --> pressure fluctuations increase in amplitude
• When cuff pressure = mean arterial BP
  --> amplitude of fluctuations peaks
• When cuff pressure < DBP
  --> pressure fluctuation disappears

Setup

• Cuff
• Tubing
• Device for inflation
• Device for gradual deflation
• Transducer for measuring pressure and oscillation in cuff
• Display

Method

The cuff is applied around the arm and inflated above systolic pressure. The cuff is then deflated in steps of 3 to 6 mmHg

Accuracy

• MABP is the most accurate.
• DBP is least accurate.

Sources of errors

• Inappropriate cuff size
• Irregular heart rhythm (e.g. AF)
• Patient movement (esp. shivering)
• Low output state
• Inaccurate calibration

Disadvantage

• No continuous readings
• Tend to overestimate at low arterial pressures

 

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