How often should oscillometric devices be calibrated?

Calibration of Oscillometric Blood Pressure Devices

Oscillometric blood pressure devices should be checked for accuracy annually, but unlike aneroid sphygmomanometers, they do not require frequent calibration as the accuracy of their pressure measurement mechanism does not deteriorate over time. 1

Differences Between Device Types

• Oscillometric devices have become the clinical standard for blood pressure measurement due to environmental concerns about mercury toxicity, greater convenience, and cost savings 1
• Unlike aneroid sphygmomanometers which require frequent calibration, oscillometric devices maintain their accuracy over time 1
• Oscillometric devices compute mean arterial pressure using oscillation amplitude and then estimate systolic and diastolic blood pressure 1

Validation Requirements

• All blood pressure monitors should be validated according to standardized protocols before clinical use 1
• Only devices that have passed validation tests such as those from the Association for the Advancement of Medical Instrumentation (AAMI), British Hypertension Society (BHS), or the International Protocol should be used in practice 1
• National and international organizations provide lists of validated monitors (e.g., www.stridebp.org, www.validatebp.org) 1, 2

Initial and Ongoing Accuracy Verification

• When a patient purchases an oscillometric monitor, they should bring it to their healthcare provider to verify both the patient's technique and the device's accuracy 1
• This verification procedure should be repeated annually 1
• The accuracy of oscillometric devices can be checked by connecting them to a mercury column or electronic testing device with a Y-tube, or by comparing readings against those taken with the auscultatory method 1, 3

Special Considerations

• Oscillometric devices may not work well in patients with atrial fibrillation or other arrhythmias 1
• Most oscillometric devices have not been validated in patients with chronic kidney disease 1
• The fact that a device passed a validation test does not guarantee accurate readings in all patients - there can be substantial individual variations, particularly in elderly or diabetic patients 1
• Using an inappropriate cuff size (too small overestimates, too large underestimates blood pressure) should be avoided 2

Clinical Impact of Device Accuracy

• Replacing mercury sphygmomanometers with validated oscillometric devices may result in different treatment decisions in approximately 5% of cases 4
• Patient-specific oscillometric methods may provide more accurate measurements in patients with large artery stiffening 5
• The precision errors for oscillometric devices can range from 6.3 to 7.6 mmHg, with higher errors in patients with high pulse pressure (>50 mmHg) 5

By following these guidelines for oscillometric device calibration and validation, clinicians can ensure accurate blood pressure measurements, leading to appropriate diagnosis and management of hypertension.