Non-Invasive Mapping of Cerebral Autoregulation Using Near Infrared Spectroscopy

Non-Invasive Mapping of Cerebral Autoregulation Using Near Infrared Spectroscopy

The investigators propose to employ advanced multi-channel near non-invasive near infrared spectroscopy (NIRS) system married with entirely non-invasive continuous arterial blood pressure (niABP) monitor to create a new wearable and portable imaging system that derives CA maps of the entire brain with high sampling rates at each point.

The objectives of this project are as follows:

1. To perform in vivo testing and optimization of the device using a block-trial design to evaluate the CA mapping system's performance during various perturbations.
2. To explore the impact of aging and sex on regional disparities in CA in a healthy volunteer population using static recording along with perturbation testing.

Objective 1:

To assess functionality and feasibility of real-time application in humans, in vivo testing will occur on a small population (n=50) of healthy human volunteers. Such work will investigate feasibility of the combination monitoring setup, optimal NIRS channel placement using the adjustable OxyMon NIRS cap, ability for pipelines to extract and analyze signals in real time for continuous derivation of NIRS-based CVR metrics at each channel and functionality of CVR map generation in real-time. Finally, the investigators will investigate perturbations to system through a series of testing (block design separated by baseline rest): A. transient hyperemic response testing via carotid compression methods, B. orthostatic challenge responses (lying-to-sit, sit-to-stand), C. vascular chemo-reactivity via fast and slow breathing exercises and D. impact of neurovascular coupling through cognitive/Stroop testing. Work here will establish areas for improvement in real time. The testing and optimization phase will last 18 months. The addition of single rSO2 channel from commercial NIRS will be used to provide a "gold standard" data stream to compare our results to.

Objective 2:

Current understanding of the aging process and sex on continuously assessed CA, and regional disparities, has been hampered by a lack of high-resolution platform. The investigators will evaluate the impact of both age and sex on CA using the newly developed platform through static CA assessments in 200 healthy volunteers. Within the 1-hour period, volunteers will have their age and sex recorded in a de-identified electronic database, have an hour of non-invasive simultaneous 24 Channel OxyMon NIRS , Finapres NOVA ABP, and single channel commercial NIRS rSO2 recording which is divided into static resting state recording and perturbation testing. This will facilitate the derivation of a normative reference range for CA using the platform along with making the dataset richer. Static resting state assessments will be done over the first half hour and in second half hour, perturbations to system will be investigated through a series of testing separated by baseline rest: A. orthostatic challenge responses (lying-to-sit, sit-to-stand), B. vascular chemo-reactivity via fast and slow breathing exercises and C. impact of neurovascular coupling through Stroop testing. The addition of single rSO2 channel from commercial NIRS will be used to provide a "gold standard" data stream to compare our results to.

Inclusion Criteria:

• Healthy volunteers (male and female)
• Age > 17

Exclusion Criteria:

• History of neurological illness
• History of systemic vascular
• History of cerebrovascular disease