Measurement of Central Aortic Pulse Pressure: Noninvasive Brachial Cuff-Based Estimation by a Transfer Function Vs. a Novel Pulse Wave Analysis Method

1] The Joanna Briggs Institute, Faculty of Health Sciences, The University of Adelaide, Adelaide, Australia [2] Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan [3] Cardiovascular Research Center, National Yang-Ming University, Taipei, Taiwan [4] Department of Medicine, National Yang-Ming University, Taipei, Taiwan.
American Journal of Hypertension (Impact Factor: 2.85). 08/2012; 25(11):1162-9. DOI: 10.1038/ajh.2012.116
Source: PubMed


The prognostic value of central aortic pulse pressure (PP-C) may have been underestimated due to its measurement inaccuracy. We aimed to investigate the accuracy of noninvasive brachial cuff-based estimation of PP-C by a generalized transfer function (GTF) or a novel pulse wave analysis (PWA) approach to directly estimate PP-C.Methods
Invasive high-fidelity right brachial and central aortic pressure tracings, and left brachial pulse volume plethysmography (PVP) waveforms from an oscillometric blood pressure (BP) monitor were all digitized simultaneously in 40 patients during cardiac catheterization. An aortic-to-brachial GTF and a PWA multivariate prediction model using the PVP waveforms calibrated to brachial cuff systolic BP (SBP) and diastolic BP(DBP) were constructed. Accuracy of the two methods was examined in another 100 patients against invasively measured PP-C.ResultsThe error of cuff PP in estimating PP-C was 1.8 ± 12.4 mm Hg. Application of the GTF on noninvasively calibrated PVP waveforms produced reconstructed aortic pressure waves and PP-C estimates with errors of -3.4 ± 11.6 mm Hg (PP-C = reconstructed aortic SBP - aortic DBP) and -2.3 ± 11.4 mm Hg (PP-C = reconstructed aortic SBP - cuff DBP), respectively. The observed systematic errors were proportional to the magnitudes of PP-C. In contrast, the error of the PWA prediction model was 3.0 ± 7.1 mm Hg without obvious proportional systematic error.Conclusions
Large random and systematic errors are introduced into the PP-C estimates when PP-C is calculated as the difference between the estimated central SBP and central or cuff DBP. The accuracy can be improved substantially with the novel PWA approach.American Journal of Hypertension 2012; doi:10.1038/ajh.2012.116.

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    ABSTRACT: Background: The superiority of prognostic value of blood pressure (BP) measured at central aorta (CBP) over conventional brachial BP measured by cuff-based BP monitors has reignited the development of new noninvasive techniques for estimating CBP. The present study validated the accuracy of CBP measured by a newly developed stand-alone CBP monitor. Methods: The CBP monitor provided readings of brachial systolic BP (SBP), brachial diastolic BP (DBP), central SBP, and central pulse pressure (PP). Brachial PP and central DBP were calculated from the relevant readings. The accuracy of the brachial and central SBP, PP, and DBP was validated against the simultaneously recorded invasively measured central aortic SBP, PP, and DBP, according to the invasive standard requirements for the noninvasive brachial BP monitors from the Association for the Advancement of Medical Instrumentation (AAMI) in 85 subjects (255 measurements; age range, 30-93 years). Results: The mean differences of cuff BP with reference to the invasively measured central SBP, PP, and DBP were -2.6 ± 9.0, -8.6 ± 11.2, and 6.1 ± 7.0 mm Hg, respectively, with the former two being obviously underestimated at high CBP and overestimated at low CBP. In contrast, the corresponding differences for the central SBP, PP, and DBP measured by the CBP monitor were -0.6 ± 5.5, -0.4 ± 7.0, and -0.2 ± 6.5 mm Hg, respectively, without obvious systematic bias. The distribution of measurement errors for central SBP, PP, and DBP surpassed the AAMI criteria. Conclusion: Central SBP, PP, and DBP can be measured accurately by a stand-alone automatic BP monitor.
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    ABSTRACT: Oscillometric central blood pressure (CBP) monitors have emerged as a new technology for blood pressure (BP) measurements. With a newly proposed diagnostic threshold for CBP, we investigated the diagnostic performance of a novel CBP monitor. We recruited a consecutive series of 138 subjects (aged 30-93 years) without previous use of antihypertensive agents for simultaneous invasive and noninvasive measurements of BP in a catheterization laboratory. With the cutoff (CBP ≥130/90mm Hg) for high blood pressure (HBP), the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the novel CBP monitor were calculated with reference to the measured CBP. In comparison, the diagnostic performance of the conventional cuff BP was also evaluated. The noninvasive CBP for detecting HBP in a sample with a prevalence of 52% showed a sensitivity of 93% (95% confidence interval (CI) = 91-95), specificity of 95% (95% CI = 94-97), PPV of 96% (95% CI = 94-97), and NPV of 93% (95% CI = 90-95). In contrast, with cuff BP and the traditional HBP criterion (cuff BP ≥140/90mm Hg), the sensitivity, specificity, PPV, and NPV were 49% (95% CI = 44-53), 94% (95% CI = 92-96), 90% (95% CI = 86-93), and 63% (95% CI 59-66), respectively. A stand-alone oscillometric CBP monitor may provide CBP values with acceptable diagnostic accuracy. However, with reference to invasively measured CBP, cuff BP had low sensitivity and NPV, which could render possible management inaccessible to a considerable proportion of HBP patients, who may be identifiable through noninvasive CBP measurements from the CBP monitor.
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