Summary

Diffuse correlation spectroscopy (DCS) measures temporal diffusing field auto-correlation function intending to get information about deep (>1 cm) tissue blood flow. DCS is a non-invasive and safe neuromonitor and, of particular interest, is used to study the cerebral blood flow (CBF) response to a mild change of the head-of-bed (HoB) position, i.e. an orthostatic challenge. This response in adults has been shown to be a biomarker of cerebral health in a variety of scenarios such as in acute ischemic stroke patients as it is a measure of cerebrovascular reactivity (CVRe). Healthy CVRe is hypothesized to be a critical determinant of brain health. Since the physiology of the hemodynamic response to this challenge is not completely clear, in this study, we aimed to reveal more details about it using fast DCS. Recently, improved instrumentation and signal-to-noise ratio allowed researchers to resolve the changes of CBF due to the pulsatile hemodynamics of the cardiac cycle as a mean to reveal new biomarkers for brain monitoring. It has been shown that one of these biomarkers might be the response of pulsatility related parameters to HoB position changes. Since the reason of this response is not completely clear, in this study, we aimed to reveal more details about it using fast DCS. We have studied pulsatile cerebral blood flow response to HoB position changes and responses of pulsatility related parameters in 21 healthy volunteers. Pulsatility related parameters measured with DCS showed a response to orthostatic challenges. Then, they can be a new potential biomarker in HoB measurements for patients with brain-related diseases.