Validation of an Adaptive Transfer Function Method to Estimate the Aortic Pressure Waveform

Abstract

Aortic pulse wave reflects cardiovascular status, but, unlike the peripheral pulse wave, is difficult to be measured reliably using noninvasive techniques. Thus, the estimation of aortic pulse wave from peripheral ones is of great significance. This study proposed an adaptive transfer function (ATF) method to estimate the aortic pulse wave from the brachial pulse wave. Aortic and brachial pulse waves were derived from 26 patients who underwent cardiac catheterization. Generalized transfer functions (GTF) were derived based on the autoregressive exogenous model. Then, the GTF was adapted by its peak resonance frequency. And the optional peak resonance frequency for an individual was determined by regression formulas using brachial systolic blood pressure. The method was validated using the leave-one-out cross validation method. Compared with previous studies, the ATF method showed better performance in estimating the aortic pulse wave and predicting the feature parameters. The prediction error of the aortic systolic blood pressure and pulse pressure were 0.2 ± 3.1 and -0.9 ± 3.1 mmHg, respectively. The percentage errors of augmentation index, percentage notch amplitude, and ejection duration were -2.1 ± 32.7%, 12.4 ± 9.2%, and -2.4 ± 3.3%, respectively.

Determination of aortic pulse transit time based on waveform decomposition of radial pressure wave

“…In this study, according to the characteristics of radial artery blood flow, the decomposition of the aortic pulse wave was extended to a peripheral artery 23 . The transfer function is an important method for noninvasive data acquisition in the decomposition of the aortic pressure wave.…”

“…Although there is a variety of ways to estimate this wave, such as surrogate methods, transfer function (TF) methods, blind system identification (BSI) methods and so on, the reconstruction of the aortic pressure wave still has many drawbacks, so that useful clinical information contained in the ‘true’ aortic pressure wave may not be directly derivable from radial pressure wave. Hence, there will be mistakes in the recognition of the feature points of aortic pressure wave after reconstruction, which may result in some errors in the decomposition 23 – 25 .…”

The Noninvasive Measurement of Central Aortic Blood Pressure Waveform

“…A simplified approach for assessing CAP is the N-point moving average (NPMA) method, which is a kind of first-order low-pass filter, removing all higher frequency-related pulse wave features, which are typically related to wave reflections, Figure 1. Frequency response of GTF produced from 26 subjects (the area between the dash-dot lines is the 95% confidence interval) [29].…”

“…The fundamental assumption of the GTF method is that the relationship between central aortic and the peripheral pulse waves remains the same in different subjects or in different status of one subject, while, as mentioned before, central arterial stiffness differs with aging, hypertension, or exercise, which changes the relationship between central aortic and brachial/radial pressure waves. Several adaptive transfer function methods were proposed trying to tune the generalized transfer function and derive more reliable CAP [29,40].…”

“…A and B indicate the peaks of the desired ATF and GTF, respectively. M and n are the peak resonance frequencies of the desired ATF and the GTF, respectively[29].Blood Pressure -From Bench to Bed…”