Comparison between an automated and manual sphygmomanometer in a population survey

Abstract

Background: An automated sphygmomanometer, the BpTRU, was used in a blood pressure (BP) survey of 2,551 residents in the province of Ontario. Automated BP readings were compared with measurements taken by a mercury sphygmomanometer under standardized conditions in a random 10% sample.

Methods: BP was recorded in 238 individuals in random order using both a standard mercury device and an automated BP recorder, the BpTRU. All subjects rested for 5 min prior to the first BP reading, which was then discarded. The mean of the next three readings was obtained using the mercury device whereas the BpTRU was set to record a mean of five readings taken at 1 min intervals with subjects resting alone in a quiet room.

Results: The mean s.d. BP with the automated device was 115 +/- 16/71 +/- 10 mm Hg compared to 118 +/- 16/74 +/- 10 mm Hg for the manual BP (P < 0.001). A systolic BP > or = 140 mm Hg was present for 16 automated and 19 manual readings. Similarly, the diastolic BP was > or = 90 mm Hg for 9 automated and 14 manual readings. Linear regression analysis showed that automated BP was a significant (P < 0.001) predictor of both manual systolic and diastolic BP.

Conclusion: Conventional manual BP readings can be replaced by readings taken using a validated, automated BP recorder in population surveys. The slightly lower readings obtained with the BpTRU device (in the context of reduced observer-subject interaction) may be a more accurate estimate of BP status.