Estimation of Mean Blood Pressure from Oscillometric and Manual Methods

The aim of this study was to estimate mean blood pressure from oscillometric and manual methods. Ten healthy subjects were studied with three repeat blood pressure measurements. Manual systolic and diastolic blood pressures (SBP and DBP) were obtained by two trained observers. During the measurement the oscillometric cuff pressure waveform was recorded digitally. The cuff pressure corresponding to the largest oscillometric pulse pressure was taken as the mean arterial pressure (AMP). AMP was also estimated from manual DBP plus one third the pressure change from DBP to SBP. Blood pressure measurement variability and the difference between automated and manual MAP were quantified. The overall coefficients of variabilily for manual SBP and DBP were 2.2% and 4.5%. Corresponding values for manual and automated MAP were 3.1% and 3.7%. The automated MAP, as a percentage of the difference between manual DBP and SBP was 28 +/- 14% (mean SD), which was lower than the classically assumed mean value of 33%. In conclusion, the relationship between MAP and SBP and DBP is complex with a large between-subject SD variability of 14%.