A Portable Optical Flow-Oximeter for Assessment of Cerebal Hemodynamics and Metabolism During Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is associated with fluctuations in blood pressure, hypercapnia, and cerebral blood flow (CBF). These perturbations can adversely affect CBF autoregulation and tissue metabolism, leading to physiological impairment or brain dysfunction. Advancing diagnostic technologies that elucidate information about physiological changes during those events would result in new insights about the pathophysiology of OSA-induced cerebral impairments and diseases (e.g., cognitive defect, stroke) and allow for individualized medical management based on the underlying pathophysiology. Although techniques exist to study cerebral metabolism such as MRI and PET, the routine use of these techniques is limited due to availability, expense, and difficulty to use at the bedside. Optical signals, however, provide an exciting alternative to costly MRI and PET measurements. We have been developing diffuse optical techniques and specifically, have pioneered the development of a novel optical approach: diffuse correlation spectroscopy (DCS). DCS measures the speckle fluctuations of diffuse light in tissue, which are sensitive to the motion of red blood cells in cerebral microvasculature (CBF). The goal of this study is to advance this technology by developing a high-throughput and portable device to simultaneously monitor CBF, cerebral oxygenation, and oxygen metabolism. We will add a secondary laser to a DCS flowmeter to measure light intensities at two wavelengths to extract oxygen and metabolic information (Aim 1). We will then calibrate and validate this DCS flow-oximeter on tissue phantoms and in human brains (Aim 2). Measurement sensitivity to hemodynamic and metabolic impairments will be tested in patients with OSA during overnight sleep and during physiological manipulations (Aim 3). Our long-term goal is to commercialize the portable DCS flow-oximeter for routine clinical use to monitor cerebral physiology at the bedside and for extensive studies in a variety of cerebral disease/injury states and therapies. Study outcomes have the potential to overcome the limitations of currently well-established imaging techniques (e.g., MRI, PET). Given the health burden of cerebrovascular events across a range of serious chronic conditions, this technology development project may significantly advance understanding of a range of cerebral impairments linked to oxygenation and metabolism, ultimately leading to significant improvements in human health.