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Rapid pressure-to-flow dynamics of cerebral autoregulation induced by instantaneous changes of arterial CO2

Rapid pressure-to-flow dynamics of cerebral autoregulation induced by instantaneous changes of arterial CO2
Rapid pressure-to-flow dynamics of cerebral autoregulation induced by instantaneous changes of arterial CO2
Continuous assessment of CA is desirable in a number of clinical conditions, where cerebral hemodynamics may change within relatively short periods. In this work, we propose a novel method that can improve temporal resolution when assessing the pressure-to-flow dynamics in the presence of rapid changes in arterial CO2. A time-varying multivariate model is proposed to adaptively suppress the instantaneous effect of CO2 on CBFV by the recursive least square (RLS) method. Autoregulation is then quantified from the phase difference (PD) between arterial blood pressure (ABP) and CBFV by calculating the instantaneous PD between the signals using the Hilbert transform (HT). A Gaussian filter is used prior to HT in order to optimize the temporal and frequency resolution and show the rapid dynamics of cerebral autoregulation. In 13 healthy adult volunteers, rapid changes of arterial CO2 were induced by rebreathing expired air, while simultaneously and continuously recording ABP, CBFV and end-tidal CO2 (ETCO2). Both simulation and physiological studies show that the proposed method can reduce the transient distortion of the instantaneous phase dynamics caused by the effect of CO2 and is faster than our previous method in tracking time-varying autoregulation. The normalized mean square error (NMSE) of the predicted CBFV can be reduced significantly by 38.7% and 37.7% (p < 0.001) without and with the Gaussian filter applied, respectively, when compared with the previous univariate model. These findings suggest that the proposed method is suitable to track rapid dynamics of cerebral autoregulation despite the influence of confounding covariates.
cerebral hemodynamics, multivariate model, adaptive filters, hilbert transform
1350-4533
1636-1643
Liu, Jia
0b8a8611-d480-4611-9c81-e5a9e5eea30e
Simpson, David M.
53674880-f381-4cc9-8505-6a97eeac3c2a
Kouchakpour, Hesam
ded5bbac-2ada-4e3e-90ef-3e088a743fa6
Panerai, Ronney B.
7acaf714-a17c-4df2-a1f3-b148c1445517
Chen, Jie
7181526d-ec25-480e-a35e-37bf4616e131
Gao, Shan
705ab680-92fa-489b-b856-6d782b7ec052
Zhang, Pandeng
8c668d6d-f634-4a2d-858b-05dc01101097
Wu, Xinyu
20c77546-697c-489a-a070-f8db09962125
Liu, Jia
0b8a8611-d480-4611-9c81-e5a9e5eea30e
Simpson, David M.
53674880-f381-4cc9-8505-6a97eeac3c2a
Kouchakpour, Hesam
ded5bbac-2ada-4e3e-90ef-3e088a743fa6
Panerai, Ronney B.
7acaf714-a17c-4df2-a1f3-b148c1445517
Chen, Jie
7181526d-ec25-480e-a35e-37bf4616e131
Gao, Shan
705ab680-92fa-489b-b856-6d782b7ec052
Zhang, Pandeng
8c668d6d-f634-4a2d-858b-05dc01101097
Wu, Xinyu
20c77546-697c-489a-a070-f8db09962125

Liu, Jia, Simpson, David M., Kouchakpour, Hesam, Panerai, Ronney B., Chen, Jie, Gao, Shan, Zhang, Pandeng and Wu, Xinyu (2014) Rapid pressure-to-flow dynamics of cerebral autoregulation induced by instantaneous changes of arterial CO2. Medical Engineering & Physics, 36 (12), 1636-1643. (doi:10.1016/j.medengphy.2014.09.005). (PMID:25287624)

Record type: Article

Abstract

Continuous assessment of CA is desirable in a number of clinical conditions, where cerebral hemodynamics may change within relatively short periods. In this work, we propose a novel method that can improve temporal resolution when assessing the pressure-to-flow dynamics in the presence of rapid changes in arterial CO2. A time-varying multivariate model is proposed to adaptively suppress the instantaneous effect of CO2 on CBFV by the recursive least square (RLS) method. Autoregulation is then quantified from the phase difference (PD) between arterial blood pressure (ABP) and CBFV by calculating the instantaneous PD between the signals using the Hilbert transform (HT). A Gaussian filter is used prior to HT in order to optimize the temporal and frequency resolution and show the rapid dynamics of cerebral autoregulation. In 13 healthy adult volunteers, rapid changes of arterial CO2 were induced by rebreathing expired air, while simultaneously and continuously recording ABP, CBFV and end-tidal CO2 (ETCO2). Both simulation and physiological studies show that the proposed method can reduce the transient distortion of the instantaneous phase dynamics caused by the effect of CO2 and is faster than our previous method in tracking time-varying autoregulation. The normalized mean square error (NMSE) of the predicted CBFV can be reduced significantly by 38.7% and 37.7% (p < 0.001) without and with the Gaussian filter applied, respectively, when compared with the previous univariate model. These findings suggest that the proposed method is suitable to track rapid dynamics of cerebral autoregulation despite the influence of confounding covariates.

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More information

Accepted/In Press date: 7 September 2014
e-pub ahead of print date: 5 October 2014
Published date: December 2014
Keywords: cerebral hemodynamics, multivariate model, adaptive filters, hilbert transform
Organisations: Human Sciences Group, Inst. Sound & Vibration Research, Faculty of Engineering and the Environment

Identifiers

Local EPrints ID: 388809
URI: http://eprints.soton.ac.uk/id/eprint/388809
ISSN: 1350-4533
PURE UUID: 32e619a9-f7f1-4a8f-bdd9-90653d5906eb

Catalogue record

Date deposited: 03 Mar 2016 14:07
Last modified: 10 Sep 2019 16:30

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