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Near-infrared spectroscopy-based system for assessment of cerebrovascular activity during stress

Cerebral blood flow (CBF) dysregulation has been implicated in a wide variety of conditions. Cerebrovascular reactivity (CVR) to CO2 may be a biomarker of CBF dysregulation. NIRS-measured regional cerebral tissue oxygen saturation (rSO2) is a non-invasive measurement made with portable and relatively inexpensive devices. We previously reported that monitoring rSO2 can identify changes in cerebrovascular dynamics in response to hypercapnic breathing challenges. The present study builds on this work, employing rSO2 to characterize changes in CBF correlates during hypercapnic breathing challenges, with a new focus on correlations with NIRS-measured vital signs. A custom breathing circuit was used to deliver a series of hypercapnic breathing challenges and recovery periods to healthy young adult subjects grouped into three exercise factors. Change in rSO2 from intra- to pre-challenge (ΔrSO2) correlated positively with change in heart rate (ΔHRhyp). Athletes showed higher ∆HRhyp than casual and non-exercisers. We previously established that athletes showed higher ΔrSO2 responses to hypercapnic breathing challenges. While the relationships between ΔrSO2 and ΔHRhyp and change in end tidal CO2 (ΔPETCO2) in response to hypercapnic breathing challenges appears to be in tact in the healthy young adults studied, and more pronounced in athletes, these relationships may not be preserved in cases of compromised CVR. Change in respiration rate correlated negatively with ΔPETCO2. Establishing baseline values of rSO2, PETCO2, HR, and RR may be useful in identifying changes in an individual’s CVR. Combined monitoring of rSO2, PETCO2, HR, and RR presents a portable, inexpensive, noninvasive NIRS-based modality for detecting changes in cerebrovascular health.