Volume 13, Issue 11 e202000173
FULL ARTICLE

Characterizing near-infrared spectroscopy signal under hypercapnia

Ho-Ching (Shawn) Yang

Ho-Ching (Shawn) Yang

Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA

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Zhenhu Liang

Zhenhu Liang

Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA

Institute of Electrical Engineering, Yanshan University, Qinhuangdao, China

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Nicole L. Vike

Nicole L. Vike

Department of Basic Medical Sciences, Purdue University, West Lafayette, Indiana, USA

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Taylor Lee

Taylor Lee

School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, USA

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Joseph V. Rispoli

Joseph V. Rispoli

Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA

School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana, USA

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Eric A. Nauman

Eric A. Nauman

Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA

School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, USA

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Thomas M. Talavage

Thomas M. Talavage

Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA

School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana, USA

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Yunjie Tong

Corresponding Author

Yunjie Tong

Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA

Correspondence

Yunjie Tong, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA.

Email: [email protected]

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First published: 24 July 2020
Citations: 7

Funding information: National Science Foundation, Grant/Award Number: Graduate Research Fellowship (NSF GRFP DGE-1333468); Indiana Clinical and Translational Sciences Institute, Grant/Award Number: the Pilot Funding for Research Use of Core Facilit; National Institutes of Health, Grant/Award Number: K25 DA031769 (YT)

Abstract

Vasoactive stress tests (i.e. hypercapnia, elevated partial pressure of arterial CO2 [PaCO2]) are commonly used in functional MRI (fMRI), to induce cerebral blood flow changes and expose hidden perfusion deficits in the brain. Compared with fMRI, near-infrared spectroscopy (NIRS) is an alternative low-cost, real-time, and non-invasive tool, which can be applied in out-of-hospital settings. To develop and optimize vasoactive stress tests for NIRS, several hypercapnia-induced tasks were tested using concurrent-NIRS/fMRI on healthy subjects. The results indicated that the cerebral and extracerebral reactivity to elevated PaCO2 depended on the rate of the CO2 increase. A steep increase resulted in different cerebral and extracerebral reactivities, leading to unpredictable NIRS measurements compared with fMRI. However, a ramped increase, induced by ramped-CO2 inhalation or breath-holding tasks, induced synchronized cerebral, and extracerebral reactivities, resulting in consistent NIRS and fMRI measurements. These results demonstrate that only tasks that increase PaCO2 gradually can produce reliable NIRS results.image

CONFLICT OF INTEREST

The authors have no conflict of interest.

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