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Spectra of data sampled at frequency-modulated rates in application to cardiovascular signals: Part 1. Analytical

B J TenVoorde1, J C Faes, O Rompelman

  • 1Vrije Universiteit, AZVU-Poli, Amsterdam, The Netherlands.

Medical & Biological Engineering & Computing
|January 1, 1994
PubMed

Insights

Pulse frequency modulation (PFM) from heart rate variations can create spurious components in cardiovascular signal analysis. Spectral analysis of systolic blood pressure may include up to 30% artifact due to PFM.

Area of Science:

  • Biomedical Engineering
  • Signal Processing
  • Cardiovascular Physiology

Background:

  • Beat-to-beat cardiovascular signals, like systolic pressure, are time series.
  • These signals exhibit pulse amplitude modulation (PAM) and pulse frequency modulation (PFM).
  • PFM, caused by heart rate variability, leads to non-uniform time spacing, complicating spectral analysis.

Purpose of the Study:

  • To derive an analytical expression for the spectrum of sinusoids sampled by a pulse frequency modulator.
  • To understand and quantify the influence of PFM on the spectral analysis of PAM signals.
  • To assess the impact of heart rate modulation on the accuracy of cardiovascular signal quantification.

Main Methods:

  • Developed an analytical expression for the spectrum of sinusoids modulated by a linear integral pulse frequency modulator (IPFM).
  • Analyzed the resulting spectral components based on the interplay between PAM and PFM frequencies.
  • Investigated the appearance of spectral components around the mean pulse frequency (mean heart rate).

Main Results:

  • Two primary spectral components emerge at the difference and sum of PFM and PAM frequencies (fp ± fx).
  • The amplitudes of these components are directly proportional to the PFM modulation depth.
  • A cluster of spectral components appears around the mean pulse frequency (fo), specifically at fo-nfp ± fx, potentially interfering with the true signal band.

Conclusions:

  • PFM introduces significant artifacts into the spectral analysis of cardiovascular signals.
  • The amplitude spectrum of systolic blood pressure can contain 20-30% spurious components due to heart rate modulation.
  • Accurate quantification of PAM requires accounting for the effects of PFM.

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