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Applying time-frequency analysis to assess cerebral autoregulation during hypercapnia

OBJECTIVE: Classic methods for assessing cerebral autoregulation involve a transfer function analysis performed using the Fourier transform to quantify relationship between fluctuations in arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV). This approach usually assumes the signal...

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Autores principales: Placek, Michał M., Wachel, Paweł, Iskander, D. Robert, Smielewski, Peter, Uryga, Agnieszka, Mielczarek, Arkadiusz, Szczepański, Tomasz A., Kasprowicz, Magdalena
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5531479/
https://www.ncbi.nlm.nih.gov/pubmed/28750024
http://dx.doi.org/10.1371/journal.pone.0181851
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author Placek, Michał M.
Wachel, Paweł
Iskander, D. Robert
Smielewski, Peter
Uryga, Agnieszka
Mielczarek, Arkadiusz
Szczepański, Tomasz A.
Kasprowicz, Magdalena
author_facet Placek, Michał M.
Wachel, Paweł
Iskander, D. Robert
Smielewski, Peter
Uryga, Agnieszka
Mielczarek, Arkadiusz
Szczepański, Tomasz A.
Kasprowicz, Magdalena
author_sort Placek, Michał M.
collection PubMed
description OBJECTIVE: Classic methods for assessing cerebral autoregulation involve a transfer function analysis performed using the Fourier transform to quantify relationship between fluctuations in arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV). This approach usually assumes the signals and the system to be stationary. Such an presumption is restrictive and may lead to unreliable results. The aim of this study is to present an alternative method that accounts for intrinsic non-stationarity of cerebral autoregulation and the signals used for its assessment. METHODS: Continuous recording of CBFV, ABP, ECG, and end-tidal CO(2) were performed in 50 young volunteers during normocapnia and hypercapnia. Hypercapnia served as a surrogate of the cerebral autoregulation impairment. Fluctuations in ABP, CBFV, and phase shift between them were tested for stationarity using sphericity based test. The Zhao-Atlas-Marks distribution was utilized to estimate the time—frequency coherence (TFCoh) and phase shift (TFPS) between ABP and CBFV in three frequency ranges: 0.02–0.07 Hz (VLF), 0.07–0.20 Hz (LF), and 0.20–0.35 Hz (HF). TFPS was estimated in regions locally validated by statistically justified value of TFCoh. The comparison of TFPS with spectral phase shift determined using transfer function approach was performed. RESULTS: The hypothesis of stationarity for ABP and CBFV fluctuations and the phase shift was rejected. Reduced TFPS was associated with hypercapnia in the VLF and the LF but not in the HF. Spectral phase shift was also decreased during hypercapnia in the VLF and the LF but increased in the HF. Time-frequency method led to lower dispersion of phase estimates than the spectral method, mainly during normocapnia in the VLF and the LF. CONCLUSION: The time—frequency method performed no worse than the classic one and yet may offer benefits from lower dispersion of phase shift as well as a more in-depth insight into the dynamic nature of cerebral autoregulation.
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spelling pubmed-55314792017-08-07 Applying time-frequency analysis to assess cerebral autoregulation during hypercapnia Placek, Michał M. Wachel, Paweł Iskander, D. Robert Smielewski, Peter Uryga, Agnieszka Mielczarek, Arkadiusz Szczepański, Tomasz A. Kasprowicz, Magdalena PLoS One Research Article OBJECTIVE: Classic methods for assessing cerebral autoregulation involve a transfer function analysis performed using the Fourier transform to quantify relationship between fluctuations in arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV). This approach usually assumes the signals and the system to be stationary. Such an presumption is restrictive and may lead to unreliable results. The aim of this study is to present an alternative method that accounts for intrinsic non-stationarity of cerebral autoregulation and the signals used for its assessment. METHODS: Continuous recording of CBFV, ABP, ECG, and end-tidal CO(2) were performed in 50 young volunteers during normocapnia and hypercapnia. Hypercapnia served as a surrogate of the cerebral autoregulation impairment. Fluctuations in ABP, CBFV, and phase shift between them were tested for stationarity using sphericity based test. The Zhao-Atlas-Marks distribution was utilized to estimate the time—frequency coherence (TFCoh) and phase shift (TFPS) between ABP and CBFV in three frequency ranges: 0.02–0.07 Hz (VLF), 0.07–0.20 Hz (LF), and 0.20–0.35 Hz (HF). TFPS was estimated in regions locally validated by statistically justified value of TFCoh. The comparison of TFPS with spectral phase shift determined using transfer function approach was performed. RESULTS: The hypothesis of stationarity for ABP and CBFV fluctuations and the phase shift was rejected. Reduced TFPS was associated with hypercapnia in the VLF and the LF but not in the HF. Spectral phase shift was also decreased during hypercapnia in the VLF and the LF but increased in the HF. Time-frequency method led to lower dispersion of phase estimates than the spectral method, mainly during normocapnia in the VLF and the LF. CONCLUSION: The time—frequency method performed no worse than the classic one and yet may offer benefits from lower dispersion of phase shift as well as a more in-depth insight into the dynamic nature of cerebral autoregulation. Public Library of Science 2017-07-27 /pmc/articles/PMC5531479/ /pubmed/28750024 http://dx.doi.org/10.1371/journal.pone.0181851 Text en © 2017 Placek et al http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
spellingShingle Research Article
Placek, Michał M.
Wachel, Paweł
Iskander, D. Robert
Smielewski, Peter
Uryga, Agnieszka
Mielczarek, Arkadiusz
Szczepański, Tomasz A.
Kasprowicz, Magdalena
Applying time-frequency analysis to assess cerebral autoregulation during hypercapnia
title Applying time-frequency analysis to assess cerebral autoregulation during hypercapnia
title_full Applying time-frequency analysis to assess cerebral autoregulation during hypercapnia
title_fullStr Applying time-frequency analysis to assess cerebral autoregulation during hypercapnia
title_full_unstemmed Applying time-frequency analysis to assess cerebral autoregulation during hypercapnia
title_short Applying time-frequency analysis to assess cerebral autoregulation during hypercapnia
title_sort applying time-frequency analysis to assess cerebral autoregulation during hypercapnia
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5531479/
https://www.ncbi.nlm.nih.gov/pubmed/28750024
http://dx.doi.org/10.1371/journal.pone.0181851
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