title: Quantification of the calibration error in the transfer function-derived central aortic blood pressures.
abstract: BACKGROUND
  The accuracy of the central aortic systolic (SBP-C) and pulse (PP-C) blood pressures estimated noninvasively by a generalized transfer function technique has been questioned. The purpose of the present study was to quantify precisely the impact of the input errors (differences between the oscillometric (SBP-O, DBP-O, PP-O) and invasive (SBP-B, DBP-B, PP-B) brachial systolic, diastolic, and pulse blood pressures) on the output errors (differences between the estimated and invasively measured SBP-C and PP-C).
  
  
  METHODS
  Invasive high-fidelity right brachial and central aortic pressure waveforms, and SBP-O, DBP-O, and PP-O (=SBP-O - DBP-O) were obtained simultaneously in 40 patients during cardiac catheterization. A generalized transfer function was applied on the individual brachial pressure waveform to derive predicted SBP-C and PP-C.
  
  
  RESULTS
  Observed input errors were -2.3 ± 5.8 mm Hg from SBP-O, 8.1 ± 5.3 mm Hg from DBP-O, and -10.4 ± 7.1 mm Hg from PP-O, respectively. The output errors were -2.2 ± 6.4 mm Hg and -10.3 ± 8.0 mm Hg for SBP-C and PP-C, respectively, when the brachial pressure waveforms were recalibrated using SBP-O and DBP-O. The outputs were determined by the inputs according to the Equation (1): SBP-C error = 0.97 × SBP-O error + 0.03 (r = 0.88, P < 0.01); and the Equation (2): PP-C error = 0.96 × PP-O error - 0.30 (r = 0.86, P < 0.01).
  
  
  CONCLUSIONS
  Noninvasive application of the generalized transfer function techniques produces estimates of SBP-C and PP-C with errors equivalent to those of the oscillometric blood pressure monitor in the estimation of SBP-B and PP-B. The output errors can be predicted from input errors of SBP-O and DBP-O.
authors.affiliation: Department of Biomedical Engineering, Chung Yuan Christian University, Chung-Li, Taiwan.
authors.forename: Yuan-Ta
authors.initials: YT
authors.lastname: Shih
authors.forename: Hao-Min
authors.initials: HM
authors.lastname: Cheng
authors.forename: Shih-Hsien
authors.initials: SH
authors.lastname: Sung
authors.forename: Wei-Chih
authors.initials: WC
authors.lastname: Hu
authors.forename: Chen-Huan
authors.initials: CH
authors.lastname: Chen
mesh_terms: D000368:Aged; D001011:Aorta / Q000502:physiology*; D001795:Blood Pressure Determination / Q000592:standards*; D001916:Brachial Artery / Q000502:physiology; D002138:Calibration; D006328:Cardiac Catheterization / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009991:Oscillometry / Q000295:instrumentation / Q000379:methods; D015203:Reproducibility of Results