TY - JOUR

T1 - Experimental approach for testing the uncoupling between cardiovascular variability series

AU - Faes, Luca

AU - Faes, Luca

AU - Nollo, Giandomenico

AU - Antolini, Renzo

PY - 2002

Y1 - 2002

N2 - In cardiovascular variability analysis, the significance of the coupling between two series is commonly assessed by defining a zero level on the magnitude-squared coherence (MSC). Although the use of the conventional value of 0.5 does not consider the dependence of MSC estimates on the analysis parameters, a theoretical threshold Ttis available only for the weighted covariance (WC) estimator. In this study, an experimental threshold for zero coherence Tewas derived by a statistical test from the sampling distribution of MSC estimated on completely uncoupled time series. MSC was estimated by the WC method (Parzen window, spectral bandwidth B = 0.015, 0.02, 0.025, 0.03 Hz) and by the parametric autoregressive (AR) method (model order M = 4, 8, 12, 16), on time series with length L = 180, 300, 420, 540 s. Tedecreased with increasing B and L and with decreasing M (range: 0.11-0.54 for WC estimator, 0.06-0.46 for AR estimator). Values for the typical parameter settings of WC and AR estimation (B = 0.025 Hz;- M = 8; L = 300 s) were, respectively, 0.24 and 0.17. Moreover, Ttwas always higher (range: 0.12-0.65) and the results were less dependable than those for Tein defining the zero level of MSC. Thus, with the proposed method, the hypothesis of uncoupling is rejected by accounting for the parameters that affect the confidence of spectral and cross-spectral estimates. The broad applicability of this approach should favour its introduction for assessing the significance of the coupling between cardiovascular variability series.

AB - In cardiovascular variability analysis, the significance of the coupling between two series is commonly assessed by defining a zero level on the magnitude-squared coherence (MSC). Although the use of the conventional value of 0.5 does not consider the dependence of MSC estimates on the analysis parameters, a theoretical threshold Ttis available only for the weighted covariance (WC) estimator. In this study, an experimental threshold for zero coherence Tewas derived by a statistical test from the sampling distribution of MSC estimated on completely uncoupled time series. MSC was estimated by the WC method (Parzen window, spectral bandwidth B = 0.015, 0.02, 0.025, 0.03 Hz) and by the parametric autoregressive (AR) method (model order M = 4, 8, 12, 16), on time series with length L = 180, 300, 420, 540 s. Tedecreased with increasing B and L and with decreasing M (range: 0.11-0.54 for WC estimator, 0.06-0.46 for AR estimator). Values for the typical parameter settings of WC and AR estimation (B = 0.025 Hz;- M = 8; L = 300 s) were, respectively, 0.24 and 0.17. Moreover, Ttwas always higher (range: 0.12-0.65) and the results were less dependable than those for Tein defining the zero level of MSC. Thus, with the proposed method, the hypothesis of uncoupling is rejected by accounting for the parameters that affect the confidence of spectral and cross-spectral estimates. The broad applicability of this approach should favour its introduction for assessing the significance of the coupling between cardiovascular variability series.

KW - Biomedical Engineering

KW - Cardiovascular variability series

KW - Computer Science Applications1707 Computer Vision and Pattern Recognition

KW - Magnitude-squared coherence

KW - Spectral analysis

KW - Biomedical Engineering

KW - Cardiovascular variability series

KW - Computer Science Applications1707 Computer Vision and Pattern Recognition

KW - Magnitude-squared coherence

KW - Spectral analysis

UR - http://hdl.handle.net/10447/276985

M3 - Article

VL - 40

SP - 565

EP - 570

JO - MEDICAL & BIOLOGICAL ENGINEERING & COMPUTING

JF - MEDICAL & BIOLOGICAL ENGINEERING & COMPUTING

SN - 0140-0118

ER -