How to calibrate an aneroid sphygmomanometer

Written by erin watson-price
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How to calibrate an aneroid sphygmomanometer
Aneroid sphygmomanotor is the scientific name for a air-operated blood pressure cup. (blood pressure manometer studio isolated image by dinostock from Fotolia.com)

In recent years, hospitals have moved away from the use of mercury sphygmomanometers because of the health hazards that mercury poses if the apparatus breaks. Initially, some people worried that the replacement of mercury sphygmomanometers with aneroid, or gas, sphygmomanometers would not be as accurate. However according to Sustainable Hospital, organisations such as the American Heart Association and the American Medical Association still accept the use of aneroid sphygmomanometers. In addition, aneroid sphygmomanometers present far fewer technical problems and are much easier to calibrate.

Skill level:
Easy

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Things you need

  • Digital BP calibration kit
  • Pencil
  • Paper
  • Aneroid sphygmomanometer

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Instructions

  1. 1

    Remove the gauge from the aneroid sphygmomanometer (AS) and attach it to the open tubing of the digital BP calibration kit. Before the concerns of mercury exposure, aneroid were calibrated using mercury syphgmomanometers. The methods do not differ from using a digital pressure readout.

  2. 2

    Using the syringe, slowly raise the pressure. Starting at 40 mmHg on the digital readout, record the reading on the AS gauge.

  3. 3

    Continue taking readings every 20 mmHg until you reach 200 mmHg.

  4. 4

    Subtract the digital pressure reading from the readings on the AS gauge. If all readings fall within 4 mmHg, the AS is within calibration limits. If all readings deviate the same amount from the digital readout and are above 4 mmHg, this is called a linear error. If all readings deviate at various amounts, it constitutes a nonlinear error.

  1. 1

    Remove the retaining ring and glass from the AS gauge. Carefully remove the needle and dial face to reveal the bellows.

  2. 2

    Locate the concave triangle with a pin at its centre. You will use this pin to make adjustments.

  3. 3

    Fix a liner error by moving the pin toward the sides of the triangle, right or left. Make small adjustments. Fix a nonlinear error by moving the pin linearly within the triangle, up or down. Make small adjustments.

  4. 4

    Replace the dial face, needle, glass and retaining ring, and repeat the test outlined above. If the adjustment does not bring the AS to within calibration limits, repeat steps 1 to 3 of this section until you reach calibration.

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