Ambulance sphygmomanometers are frequently inaccurate

To determine the accuracy and reliability of sphygmomanometers used in a metropolitan emergency medical services (EMS) system.

As a cross-sectional, convenience sample, 150 sphygmomanometers used by EMS personnel in Milwaukee County, Wisconsin, were evaluated. Each sphygmomanometer was checked for accuracy by connecting the manometer to a new, standard mercury manometer using a "Y" connector. Pressure was checked at readings of 60, 90, 120, and 200 mm Hg. The integrity of the device (leaking) was checked by inflating the cuff around a can to 300 mm Hg and measuring the pressure lost in 1 minute. Devices were determined to be inaccurate if the average of the absolute differences at each pressure deviated by more than 3 mm Hg. The device was determined to be unreliable (leaked) if it lost pressure greater than 15 mm Hg in 1 minute.

Twenty-eight percent (41/149) of the devices were inaccurate at 90 mm Hg and 25% (37/149) were inaccurate overall. The overall and 90 mm Hg average deviations were +/- 6.6 and +/- 6.0 mm Hg, respectively. Sixty-three percent (94/150) of the devices were unreliable (leaked). When considering both accuracy and reliability at 90 mm Hg, a total of 73% (109/150) of the devices failed one or both of the criteria.

This study suggests that an accurate blood pressure measurement may not be reliably obtained with 73% of the sphygmomanometers currently used in the county's EMS system.