Automatic blood pressure measurement: the oscillometric waveform shape is a potential contributor to differences between oscillometric and auscultatory pressure measurements.
OBJECTIVE
To explore the differences between oscillometric and auscultatory measurements.


METHODS
From a simulator evaluation of a non-invasive blood pressure (NIBP) device regenerating 242 oscillometric blood pressure waveforms from 124 subjects, 10 waveforms were selected based on the differences between the NIBP (oscillometric) and auscultatory pressure measurements. Two waveforms were selected for each of five criteria: systolic over and underestimation; diastolic over and underestimation; and close agreement for both systolic and diastolic pressures. The 10 waveforms were presented to seven different devices and the oscillometric-auscultatory pressure differences were compared between devices and with the oscillometric waveform shapes.


RESULTS
Consistent patterns of waveform-dependent over and underestimation of systolic and diastolic pressures were shown for all seven devices. The mean and standard deviation, for all devices, of oscillometric-auscultatory pressure differences were: for the systolic overestimated waveforms, 36 +/- 28/-6 +/- 3 and 23 +/- 2/-1 +/- 3 mmHg (systolic/diastolic differences); for systolic underestimated waveforms, -21 +/- 5/-4 +/- 3 and -11 +/- 4/-3 +/- 3 mmHg; for diastolic overestimated waveforms, 3 +/- 4/12 +/- 5 and 17 +/- 6/10 +/- 2 mmHg; for diastolic underestimated waveforms, 1 +/- 4/-22 +/- 4 and -9 +/- 6/-29 +/- 4 mmHg; and for the two waveforms with good agreement, 0 +/- 6/0 +/- 3 and -2 +/- 4/-4 +/- 3 mmHg. Waveforms for which devices showed good oscillometric and auscultatory agreement had smooth envelopes with clearly defined peaks, compared with the broader plateau and complex shapes of those waveforms for which devices over or underestimated pressures.


CONCLUSIONS
By increasing the understanding of the characteristics and limitations of the oscillometric method and the effects of waveform shape on pressure measurements, simulator evaluation should lead to improvements in NIBP devices.
Amoore
John N
JN
Department of Medical Physics, Royal Infirmary of Edinburgh, Edinburgh, UK. john.amoore@luht.scot.nhs.uk
Lemesre
Yann
Y
Murray
Ian C
IC
Mieke
Stephan
S
King
Susan T
ST
Smith
Fiona E
FE
Murray
Alan
A
D000328:Adult; D000368:Aged; D001314:Auscultation / Q000295:instrumentation* / Q000379:methods*; D001794:Blood Pressure; D001795:Blood Pressure Determination / Q000295:instrumentation* / Q000379:methods*; D015924:Blood Pressure Monitors; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009991:Oscillometry / Q000295:instrumentation / Q000379:methods; D015203:Reproducibility of Results; D012984:Software