Carrier assisted differential detection with a generalized transfer function

This study aims to demonstrate that a comprehensive one-dimensional model of the arterial network can be used in conjunction with the generalized transfer function (GTF) technique to estimate central aortic pressure using pressure waveforms obtained from peripheral sites. The peripheral and central pressure waveforms for a healthy subject are used to estimate transfer functions, which are then used to reconstruct central aortic pressure waveforms for a second model that simulates arterial stiffening. The similarities between the simulated aortic waveform and the waveforms estimated using the transfer function are and from the brachial, carotid and iliac arteries, respectively. The root-mean-square errors (RMSE) for the reconstructed waveforms from the brachial, carotid and iliac arteries are and mmHg, respectively. The results from this study illustrate that the proposed method provides a feasible alternative to higher dimensional models as well as experimental studies and can greatly enhance the accuracy of central aortic pressure estimation.

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Effect of non-invasive calibration of radial waveforms on error in transfer-function-derived central aortic waveform characteristics

Clinical Science ◽

10.1042/cs20030294 ◽

2004 ◽

Vol 107 (2) ◽

pp. 205-211 ◽

Cited By ~ 62

Author(s):

Sarah A. HOPE ◽

Ian T. MEREDITH ◽

James D. CAMERON

Keyword(s):

Transfer Function ◽

Augmentation Index ◽

Systolic Pressure ◽

Function Estimation ◽

Non Invasive ◽

Clinical Interest ◽

Time Parameters ◽

Generalized Transfer Function ◽

The Impact ◽

Significant Underestimation

Transfer function techniques are increasingly used for non-invasive estimation of central aortic waveform characteristics. Non-invasive radial waveforms must be calibrated for this purpose. Most validation studies have used invasive pressures for calibration, with little data on the impact of non-invasive calibration on transfer-function-derived aortic waveform characteristics. In the present study, simultaneous invasive central aortic (Millar Mikro-tip® catheter transducer) and non-invasive radial (Millar® Mikro-tip® tonometer) pressure waveforms and non-invasive brachial pressures (Dinamap®) were measured in 42 subjects. In this cohort, radial waveforms were calibrated to both invasive and non-invasive mean and diastolic pressures. From each of these, central waveforms were reconstructed using a generalized transfer function obtained by us from a previous cohort [Hope, Tay, Meredith and Cameron (2002) Am. J. Physiol. Heart Circ. Physiol. 283, H1150–H1156]. Waveforms were analysed for parameters of potential clinical interest. For calibrated radial and reconstructed central waveforms, different methods of calibration were associated with differences in pressure (P<0.001), but not time parameters or augmentation index. Whereas invasive calibration resulted in little error in transfer function estimation of central systolic pressure (difference −1±8 mmHg; P=not significant), non-invasive calibration resulted in significant underestimation (7±12 mmHg; P<0.001). Errors in estimated aortic parameters differed with non-invasively calibrated untransformed radial and transfer-function-derived aortic waveforms (all P<0.01), with smaller absolute errors with untransformed radial waveforms for most pressure parameters [systolic pressure, 5±16 and 7±12 mmHg; pulse pressure, 0±16 and 4±12 mmHg (radial and derived aortic respectively)]. When only non-invasive pressures are accessible, analysis of untransformed radial waveforms apparently produces smaller errors in the estimation of central aortic systolic pressure, and other waveform parameters, than using a generalized transfer function.

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Generalized Transfer Function Model for Solute Transport in Heterogeneous Soils

Soil Science Society of America Journal ◽

10.2136/sssaj2000.6451595x ◽

2000 ◽

Vol 64 (5) ◽

pp. 1595-1602 ◽

Cited By ~ 11

Author(s):

Renduo Zhang

Keyword(s):

Transfer Function ◽

Solute Transport ◽

Transfer Function Model ◽

Function Model ◽

Heterogeneous Soils ◽

Generalized Transfer Function

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Generalized transfer function estimation using evolutionary spectral deblurring

IEEE Transactions on Signal Processing ◽

10.1109/78.774782 ◽

1999 ◽

Vol 47 (8) ◽

pp. 2335-2339 ◽

Cited By ~ 6

Author(s):

S.I. Shah ◽

L.F. Chaparro ◽

A. El-Jaroudi

Keyword(s):

Transfer Function ◽

Function Estimation ◽

Generalized Transfer Function

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