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Does the variability of evoked tympanic membrane displacement data (Vm) increase as the magnitude of the pulse amplitude increases?

Does the variability of evoked tympanic membrane displacement data (Vm) increase as the magnitude of the pulse amplitude increases?
Does the variability of evoked tympanic membrane displacement data (Vm) increase as the magnitude of the pulse amplitude increases?

Objectives: Evoked tympanic membrane displacement (TMD) measurements, quantified by Vm, record small volume changes in the ear canal following stimulation of the acoustic reflex. Vm shows a correlation with intracranial pressure (ICP) and has been proposed as an option to non-invasively measure ICP. The spontaneous pulsing of the tympanic membrane, driven by the cardiovascular pulse, may contaminate the recordings and contribute to high measurement variability in some subjects. This study hypothesised that the larger the spontaneous vascular pulse, the larger the variability in Vm. Materials and methods: Spontaneous and evoked TMD data from each ear in the sitting and supine position were recorded from 100 healthy volunteers using the MMS-14 CCFP analyser. ECG was also recorded to identify each heartbeat. Using bespoke software written in Matlab, spontaneous data were analysed to produce average pulse amplitude (PA) waveforms and evoked data were analysed to calculate average Vm and its standard deviation. Averaged spontaneous PA was plotted against Vm variability and Pearson’s correlation coefficient was calculated to test for a significant linear relationship. Results: There was a strong positive correlation between PA and Vm variability in all conditions: left sitting, r = 0.758; left supine, r = 0.665; right sitting, r = 0.755; right supine, r = 0.513. All were significant at p < 0.001. Conclusion: This study shows that large Vm variability is associated with a large spontaneous vascular pulse. This suggests that efforts to reduce vascular pulsing from recordings, either by a subtraction technique during post-processing or ECG-gating of the evoking stimulus, may improve reliability of the Vm measurement.

Intracranial pressure, Non-invasive, Tympanic membrane displacement, V, Vascular pulse
0065-1419
103-106
Springer
Sharif, Sammy J.
a3737f55-f322-4b76-9dc2-900242510d65
Campbell-Bell, Cherith M.
6df96d49-a4c3-4cfb-add1-4d34ff1b1ba1
Bulters, Diederik O.
d6f9644a-a32f-45d8-b5ed-be54486ec21d
Marchbanks, Robert J.
1ebe90b6-cb8a-4f9e-9585-4e264a951d7f
Birch, Anthony A.
755f2236-4c0c-49b5-9884-de4021acd42d
Heldt, T.
Sharif, Sammy J.
a3737f55-f322-4b76-9dc2-900242510d65
Campbell-Bell, Cherith M.
6df96d49-a4c3-4cfb-add1-4d34ff1b1ba1
Bulters, Diederik O.
d6f9644a-a32f-45d8-b5ed-be54486ec21d
Marchbanks, Robert J.
1ebe90b6-cb8a-4f9e-9585-4e264a951d7f
Birch, Anthony A.
755f2236-4c0c-49b5-9884-de4021acd42d
Heldt, T.

Sharif, Sammy J., Campbell-Bell, Cherith M., Bulters, Diederik O., Marchbanks, Robert J. and Birch, Anthony A. (2018) Does the variability of evoked tympanic membrane displacement data (Vm) increase as the magnitude of the pulse amplitude increases? In, Heldt, T. (ed.) Intracranial Pressure &amp; Neuromonitoring XVI. (Acta Neurochirurgica Supplement, , (doi:10.1007/978-3-319-65798-1_22), 126) Cham. Springer, pp. 103-106. (doi:10.1007/978-3-319-65798-1_22).

Record type: Book Section

Abstract

Objectives: Evoked tympanic membrane displacement (TMD) measurements, quantified by Vm, record small volume changes in the ear canal following stimulation of the acoustic reflex. Vm shows a correlation with intracranial pressure (ICP) and has been proposed as an option to non-invasively measure ICP. The spontaneous pulsing of the tympanic membrane, driven by the cardiovascular pulse, may contaminate the recordings and contribute to high measurement variability in some subjects. This study hypothesised that the larger the spontaneous vascular pulse, the larger the variability in Vm. Materials and methods: Spontaneous and evoked TMD data from each ear in the sitting and supine position were recorded from 100 healthy volunteers using the MMS-14 CCFP analyser. ECG was also recorded to identify each heartbeat. Using bespoke software written in Matlab, spontaneous data were analysed to produce average pulse amplitude (PA) waveforms and evoked data were analysed to calculate average Vm and its standard deviation. Averaged spontaneous PA was plotted against Vm variability and Pearson’s correlation coefficient was calculated to test for a significant linear relationship. Results: There was a strong positive correlation between PA and Vm variability in all conditions: left sitting, r = 0.758; left supine, r = 0.665; right sitting, r = 0.755; right supine, r = 0.513. All were significant at p < 0.001. Conclusion: This study shows that large Vm variability is associated with a large spontaneous vascular pulse. This suggests that efforts to reduce vascular pulsing from recordings, either by a subtraction technique during post-processing or ECG-gating of the evoking stimulus, may improve reliability of the Vm measurement.

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More information

e-pub ahead of print date: 1 March 2018
Published date: 2018
Keywords: Intracranial pressure, Non-invasive, Tympanic membrane displacement, V, Vascular pulse

Identifiers

Local EPrints ID: 418773
URI: http://eprints.soton.ac.uk/id/eprint/418773
ISSN: 0065-1419
PURE UUID: 48940052-b1f5-4c37-819c-01acab239bad
ORCID for Anthony A. Birch: ORCID iD orcid.org/0000-0002-2328-702X

Catalogue record

Date deposited: 22 Mar 2018 17:30
Last modified: 07 Oct 2020 02:20

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