Calibration accuracy of hospital-based non-invasive blood pressure measuring devices

Accurate blood pressure (BP) measurement is dependent on a trained observer using validated and properly maintained equipment. BP devices should be checked regularly to ensure that their calibration remains within the European Standard specification of +/- 3 mm Hg. This study assessed the air leakage rates and calibration accuracy of BP devices in use at a large teaching hospital, using a calibrated electronic pressure gauge as reference. Air leakage rates were recorded over 1 min and static pressures were recorded at 250/200/150/100/50/0 mm Hg for computer download and analysis. A total of 127 devices were assessed (18 mercury, 62 aneroid and 47 automated). In total, 22 different models of devices were available, of which 11 were automated and only 4 had published evidence of a validation using a recognized protocol (British Hypertension Society, Association for the Advancement of Medical Instrumentation or International Protocol). Only 3% (n=4) of devices had an air leakage rate within 4 mm Hg per min and 25% (n=32) of devices failed to meet the European calibration standard of +/- 3 mm Hg. Respective failure rates were 6% (1/18) for mercury, 31% (19/62) for aneroid and 26% (12/47) for automated devices. Inaccurate BP measurement of only 3 mm Hg can have detrimental effects in the patient. This study shows a quarter of devices currently in use at a large teaching hospital to have an unacceptable calibration error. Regular maintenance and calibration checks are vital in ensuring that BP is measured as accurately as possible. Journal of Human Hypertension (2010) 24, 58-63; doi: 10.1038/jhh.2009.29; published online 2 April 2009