Quantification of the calibration error in the transfer function-derived central aortic blood pressures

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering
• Medical Diagnostics

Background:

• The accuracy of noninvasive central aortic systolic (SBP-C) and pulse (PP-C) pressure estimation via generalized transfer function is debated.
• Quantifying the impact of input errors (brachial oscillometric vs. invasive) on output errors (central aortic) is crucial.

Purpose of the Study:

• To precisely quantify how input errors in brachial blood pressure measurements affect noninvasive central aortic pressure estimations.
• To assess the accuracy of generalized transfer function techniques for SBP-C and PP-C.

Main Methods:

• Simultaneous invasive measurement of central aortic and brachial pressure waveforms in 40 cardiac catheterization patients.
• Application of a generalized transfer function to brachial waveforms to derive SBP-C and PP-C.
• Comparison of oscillometric brachial pressures (SBP-O, DBP-O, PP-O) with invasive brachial pressures (SBP-B, DBP-B, PP-B).

Main Results:

• Input errors: SBP-O (-2.3 ± 5.8 mm Hg), DBP-O (8.1 ± 5.3 mm Hg), PP-O (-10.4 ± 7.1 mm Hg).
• Output errors (recalibrated): SBP-C (-2.2 ± 6.4 mm Hg), PP-C (-10.3 ± 8.0 mm Hg).
• SBP-C error = 0.97 × SBP-O error + 0.03 (r=0.88); PP-C error = 0.96 × PP-O error - 0.30 (r=0.86).

Conclusions:

• Noninvasive generalized transfer function techniques yield SBP-C and PP-C errors comparable to oscillometric brachial pressure monitors.
• Output errors in central aortic pressure estimation are predictable from input errors in oscillometric brachial systolic and diastolic pressures.