Measurement accuracy of non-invasively obtained central blood pressure by applanation tonometry: a systematic review and meta-analysis

Background and objectives: Non-invasive methods based on applanation tonometry have been proposed to estimate central blood pressure. However, the accuracy of these methods hasn't been systematically examined.

Methods: We performed a systematic review and meta-analysis of studies comparing estimated and invasively measured central BP.

Results: Sufficient data were available in 22 studies for meta-analysis (857 subjects and 1167 measurements). Acquired arterial pressure waveforms in these studies were directly measured, calibrated to match invasive aortic mean BP and diastolic BP or calibrated to match brachial BP measured with a sphygmomanometer, cuff BP. Of the former 2 conditions, the errors of estimated central BP were small with a mean and standard deviation of difference -1.1 ± 4.1 mm Hg (95% limits of agreement -9.1-6.9 mm Hg) for central systolic BP; -0.5 ± 2.1 mm Hg (-4.6-3.6 mm Hg) for central diastolic BP; and -0.8 ± 5.1 mm Hg (-10.8-9.2 mm Hg) for central pulse pressure. However, the errors inflated to -8.2 ± 10.3 mm Hg (-28.4-12.0 mm Hg) for central systolic BP, 7.6 ± 8.7 mm Hg (-9.5-24.6 mm Hg) for central diastolic BP, and -12.2 ± 10.4 mm Hg (-32.5-8.1 mm Hg) for central pulse pressure, when calibrated to cuff BP. The findings were still evident in subgroup analysis conducted with different central BP estimating methods and validated cuff BP monitors.

Conclusion: Present tonometry-based central BP estimating methods are acceptable in theory, with small errors. However, based on current available evidence, there is substantial room for improvement in measurement accuracy of central BP when cuff BP is used to calibrate the peripheral waveforms.