N-Point Moving Average: A Special Generalized Transfer Function Method for Estimation of Central Aortic Blood...

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering
• Signal Processing

Background:

• Central aortic systolic pressure (CASP) estimation is crucial for cardiovascular assessment.
• The N-point moving average (NPMA) offers a simplified approach compared to the generalized transfer function (GTF).
• The theoretical relationship and practical differences between NPMA and GTF remain underexplored.

Purpose of the Study:

• To theoretically investigate the properties of NPMA in relation to GTF.
• To explore the impact of integer versus fractional denominators in NPMA for CASP estimation.
• To validate NPMA's performance against established methods using invasive pressure waveforms.

Main Methods:

• NPMA was developed using convolution of a square wave with radial/brachial pressure waveforms.
• A tube model-based transfer function (MTF) was used for theoretical comparison.
• Invasive aortic and radial pressures were recorded from 62 subjects, with CASP estimated by NPMA, GTF, and MTF via cross-validation.

Main Results:

• Theoretical analysis revealed NPMA as an inverse constant transfer function, matching MTF at low frequencies.
• An optimized fractional denominator (K=4.4) for NPMA significantly reduced the mean difference in CASP estimation compared to an integer denominator (K=4).
• NPMA demonstrated high correlation with MTF (r²=0.99) and GTF (r²=0.97), with minimal mean differences.

Conclusions:

• NPMA is fundamentally similar in nature to the GTF for CASP estimation.
• The use of a fractional denominator in NPMA enhances its accuracy and clinical applicability.
• NPMA presents a simplified yet effective method for estimating central aortic systolic pressure.