SignificanceCerebrovascular reactivity (CVR), i.e., the ability of cerebral vasculature to dilate or constrict in response to vasoactive stimuli, is a biomarker of vascular health. Exogenous administration of inhaled carbon dioxide, i.e., hypercapnia (HC), remains the “gold-standard” intervention to assess CVR. More tolerable paradigms that enable CVR quantification when HC is difficult/contraindicated have been proposed. However, because these paradigms feature mechanistic differences in action, an assessment of agreement of these more tolerable paradigms to HC is needed.AimWe aim to determine the agreement of CVR assessed during HC, breath-hold (BH), and resting state (RS) paradigms.ApproachHealthy adults were subject to HC, BH, and RS paradigms. End tidal carbon dioxide (EtCO2) and cerebral blood flow (CBF, assessed with diffuse correlation spectroscopy) were monitored continuously. CVR (%/mmHg) was quantified via linear regression of CBF versus EtCO2 or via a general linear model (GLM) that was used to minimize the influence of systemic and extracerebral signal contributions.ResultsStrong agreement (CCC ≥ 0.69; R ≥ 0.76) among CVR paradigms was demonstrated when utilizing a GLM to regress out systemic/extracerebral signal contributions. Linear regression alone showed poor agreement across paradigms (CCC ≤ 0.35; R ≤ 0.45).ConclusionsMore tolerable experimental paradigms coupled with regression of systemic/extracerebral signal contributions may offer a viable alternative to HC for assessing CVR.
In children with sickle cell disease, there is a clinical need for non-invasive quantification of the degree of hemometabolic stress in these patients to mitigate risk of stroke. Frequency-domain near-infrared spectroscopy (FDNIRS) and diffuse correlation spectroscopy (DCS) measures of regional oxygen extraction fraction, cerebral blood flow, and cerebral metabolic rate of oxygen have potential to provide markers of cerebral metabolic stress. In this study, we characterize the intra-subject and inter-operator repeatability of these measures, and we correlate DCS measures of cerebral blood flow index against both arterial spin-labeled MRI and transcranial Doppler ultrasound in a cohort of pediatric SCD patients.
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