Are Aneroid Sphygmomanometers Accurate in Hospital and Clinic Settings?

BACKGROUND: The aneroid sphygmomanometer is commonly used for the indirect measurement of blood pressure despite significant concerns about its accuracy. Although the mercury sphygmomanometer is highly accurate, there are concerns about the environmental toxicity of mercury. In response to various external pressures to become essentially mercury free, the Mayo Clinic, Rochester, Minn, has replaced many mercury sphygmomanometers with aneroid devices. Since 1993, a maintenance protocol has been in place to ensure proper function and accuracy of these devices. METHODS: We assessed the accuracy of 283 aneroid devices using as the reference standard a digital pressure and vacuum meter that was calibrated using a mercury sphygmomanometer. RESULTS: The mean +/- SD values from the aneroid device in millimeters of mercury at each reference point (at 20-mm Hg intervals from 60 to 240 mm Hg defined by the reference device) were 59.9 +/- 1.9 at 60; 79.9 +/- 1.9 at 80; 100.0 +/- 1.8 at 100; 120.3 +/- 1.8 at 120; 140.7 +/- 1.4 at 140; 160.7 +/- 1.7 at 160; 180.9 +/- 1.3 at 180; 200.7 +/- 5.0 at 200; 221.0 +/- 1.3 at 220; and 240.8 +/- 1.6 at 240 (r = 0.99; P<.001). The values from the aneroid device underestimated those of the reference device by a mean of 0.5 mm Hg (95% confidence interval, 0.3-0.7). Virtually 100% of the values from the aneroid device were within the 4-mm Hg range recommended by the Association for the Advancement of Medical Instrumentation. CONCLUSION: Aneroid sphygmomanometers provide accurate pressure measurements when a proper maintenance protocol is followed.