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Assessment of autoregulation by means of periodic changes in blood pressure

Assessment of autoregulation by means of periodic changes in blood pressure
Assessment of autoregulation by means of periodic changes in blood pressure

BACKGROUND AND PURPOSE: The aim of this study was to test the hypothesis that the phase difference that occurs between an induced oscillation in blood pressure and the resultant oscillation in middle cerebral artery (MCA) flow velocity could reflect the competence of cerebral autoregulation.

METHODS: Fourteen volunteers performed 19 cycles of 10 seconds of squatting followed by 10 seconds of standing. Peak MCA velocity was measured with transcranial Doppler ultrasound, and blood pressure was measured with a servo-controlled finger plethysmograph held level with the head. Waveforms from each cycle were added to obtain averaged waveforms of arterial blood pressure and MCA velocity. These results were processed by Fourier analysis to extract the phase difference between the fundamental components of velocity and pressure. Each volunteer performed the exercise three times: first breathing normally, secondly hyperventilating (hypocapnia), and finally while breathing air containing 5% carbon dioxide (hypercapnia). Under these conditions the volunteers were expected to have normal, enhanced, and impaired auto-regulation, respectively.

RESULTS: The measurements made with normal breathing showed a phase lead of velocity ahead of pressure of 46 +/- 14 degrees (mean +/- SD). We noted a highly significant reduction in phase lead with hypercapnia (P < .00015) (Wilcoxon signed rank test, two-tailed) and a highly significant increase in phase lead with hypocapnia (P < .002).

CONCLUSIONS: The results support our hypothesis and may lead to a technique for assessing the competence of cerebral autoregulation.

Adolescent, Adult, Blood Flow Velocity, Blood Pressure, Cerebral Arteries, Exercise, Female, Homeostasis, Humans, Male, Journal Article
0039-2499
834-7
Birch, A.A.
755f2236-4c0c-49b5-9884-de4021acd42d
Dirnhuber, M.J.
d33f5008-5e52-4b15-b2fd-4a92acf29b61
Hartley-Davies, R.
f6edb732-1020-4b4d-8ae9-2d24edc2f95e
Iannotti, F.
9fc0f0bc-8623-4146-bdf5-ea08708506d7
Neil-Dwyer, G.
19520fec-ecd3-436f-9420-b7bd776751c3
Birch, A.A.
755f2236-4c0c-49b5-9884-de4021acd42d
Dirnhuber, M.J.
d33f5008-5e52-4b15-b2fd-4a92acf29b61
Hartley-Davies, R.
f6edb732-1020-4b4d-8ae9-2d24edc2f95e
Iannotti, F.
9fc0f0bc-8623-4146-bdf5-ea08708506d7
Neil-Dwyer, G.
19520fec-ecd3-436f-9420-b7bd776751c3

Birch, A.A., Dirnhuber, M.J., Hartley-Davies, R., Iannotti, F. and Neil-Dwyer, G. (1995) Assessment of autoregulation by means of periodic changes in blood pressure. Stroke, 26 (5), 834-7.

Record type: Article

Abstract

BACKGROUND AND PURPOSE: The aim of this study was to test the hypothesis that the phase difference that occurs between an induced oscillation in blood pressure and the resultant oscillation in middle cerebral artery (MCA) flow velocity could reflect the competence of cerebral autoregulation.

METHODS: Fourteen volunteers performed 19 cycles of 10 seconds of squatting followed by 10 seconds of standing. Peak MCA velocity was measured with transcranial Doppler ultrasound, and blood pressure was measured with a servo-controlled finger plethysmograph held level with the head. Waveforms from each cycle were added to obtain averaged waveforms of arterial blood pressure and MCA velocity. These results were processed by Fourier analysis to extract the phase difference between the fundamental components of velocity and pressure. Each volunteer performed the exercise three times: first breathing normally, secondly hyperventilating (hypocapnia), and finally while breathing air containing 5% carbon dioxide (hypercapnia). Under these conditions the volunteers were expected to have normal, enhanced, and impaired auto-regulation, respectively.

RESULTS: The measurements made with normal breathing showed a phase lead of velocity ahead of pressure of 46 +/- 14 degrees (mean +/- SD). We noted a highly significant reduction in phase lead with hypercapnia (P < .00015) (Wilcoxon signed rank test, two-tailed) and a highly significant increase in phase lead with hypocapnia (P < .002).

CONCLUSIONS: The results support our hypothesis and may lead to a technique for assessing the competence of cerebral autoregulation.

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More information

Published date: May 1995
Keywords: Adolescent, Adult, Blood Flow Velocity, Blood Pressure, Cerebral Arteries, Exercise, Female, Homeostasis, Humans, Male, Journal Article

Identifiers

Local EPrints ID: 427688
URI: https://eprints.soton.ac.uk/id/eprint/427688
ISSN: 0039-2499
PURE UUID: a25bffbe-5d9a-46f7-bd9a-26a865c79c4e
ORCID for A.A. Birch: ORCID iD orcid.org/0000-0002-2328-702X

Catalogue record

Date deposited: 25 Jan 2019 17:30
Last modified: 14 Mar 2019 01:22

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Contributors

Author: A.A. Birch ORCID iD
Author: M.J. Dirnhuber
Author: R. Hartley-Davies
Author: F. Iannotti
Author: G. Neil-Dwyer

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