Sphygmomanometers in hospital and family practice: problems and recommendations.
The accuracy and working condition of 210 sphygmomanometers were tested: 100 (50 and mercury and 50 aneroid) models were used in family practices and 100 mercury models in hospitals. Faults in the inflation-deflation system were common and caused mainly by dirt or wear in the control valves. Leakage occurred in 48% of the hospital and 33% of the family practice sphygmomanometers. In the mercury models the mercury or air vents were often in an unsatisfactory condition or the calibrated glass tube dirty. The accuracy of the gauges was examined at 90 and 150 mm Hg: fewer than 2% of the mercury sphygmomanometers but 30% of the aneroid models had errors greater than +/- 4 mm Hg at either pressure. Over half of the cuffs examined had bladders widths less than the recommended size, and 94% had bladders shorter than the length recommended for use on normal adults. Mercury sphygmomanometers should be bought in preference to aneroid models as they are more accurate, less expensive in the long term, and can be maintained by the owner; they should be checked every six to 12 months depending on usage. Replacement parts should be kept readily available.