Sources of error in non-invasive blood pressure measurement
Core concept
- Oscillometric NIBP does not measure SBP or DBP - it measures the cuff-pressure oscillation envelope and computes them
- MAP = cuff pressure at maximal oscillation amplitude (the only directly measured value)
- SBP and DBP derived by proprietary algorithm -> device- and rhythm-dependent
- Cuff size is the dominant error
- Bladder length >=80% and width >=40% of arm circumference
- Too small -> overestimation (commonest error; up to +10-30 mmHg in obesity)
- Too large -> underestimation (smaller effect)
3 more sections, plus exam facts
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