Multi-Use Near-Infrared Spectroscopy System for Spaceflight Health Applications

FINAL REPORTING--FEBRUARY 2015

Research Impact: Currently, pulse oximetry is available onboard the International Space Station (ISS), and one would expect it to be flown on future exploration class missions. A pulse oximeter, however, provides only a small subset of the information available from a NIRS measurement. In particular, pulse oximetry can only provide oxygenation measures from arterial blood in superficial tissue when a sufficiently strong pulse is available, whereas NIRS measurements can provide surface and deep arterial measurements as well as venous and whole-tissue measurements. Moreover, NIRS does not require clear pulse signals, being usable in compartment syndrome, during muscle contractions, or in patients with a weak or thready pulse. A NIRS-based imager can further provide spatial information about tissue oxygenation or perfusion. This could support: (1) assessing the relative conditioning status of (and optimizing training for) different muscle groups, (2) assessing cerebral hemodynamics for conditions such as visual impairment/intracranial pressure (VIIP), including tissue oxygenation in different tissue layers (e.g., scalp versus cerebral oxygenation, or skin versus fat versus deeper muscle layers), (3) sleep physiology studies, or even (4) identifying the location or evaluating the size of an internal hemorrhage. When deploying a sufficient number of near-infrared wavelengths and source/detector locations, one can further measure water content (e.g., edema), and correct measurements of deeper tissue layers for skin color, fat layers, and dynamic changes in systemic physiology (cardiac, respiratory, and other vasomotor interference). These capabilities of NIRS over standard pulse oximetry are not currently available in spaceflight but could be provided by NINscan-M. The oxygenation and perfusion measures just described can also be enhanced by various auxiliary measurements. For example, electrocardiography (ECG) can be combined with systemic NIRS measurements to help estimate cardiac output. Electromyography (EMG) can be combined with muscle oxygenation measures to better understand muscle endurance and conditioning. Accelerometry and temperature measures can help identify and, when needed, compensate for environmental influences on NIRS or other physiological/auxiliary measurements. The goal with NINscan-M was to provide not only shallow- and deep-tissue NIRS imaging capabilities, but also the ability to support recording of various physiological measures—each useful in their own right as well as to enhance NIRS assessment capabilities. NIRS and auxiliary functions are provided modularly, so that missions with different requirements need only pack and deploy the necessary components.

Earth Benefits: The same capabilities that are useful for exploration spaceflight are also relevant for Earth-based applications. For example, continuous non-invasive, long-duration brain monitoring for cerebral hemorrhage is key and an unmet need following neurosurgery, stroke, and traumatic brain injury. Non-invasive monitoring of brain motion within the skull is a novel capability useful both in research and prevention of traumatic brain injury, and our group is working on a project supported by the National Football League Players Association on this topic. Real-time muscle oxygenation imaging can be used to optimize elite athlete training as well as enhance rehabilitation protocols. And the entire field of human neuroscience is largely constrained to using large machines for brain function monitoring that require the subject to remain as still as possible. NINscan-M provides the ability to monitor brain function during people's daily activities, opening up entirely new domains of investigation. The NINscan-M device is expected to be useful in these and other contexts.

ANNUAL REPORTING IN OCTOBER 2014

Research Impact: Currently, pulse oximetry is available onboard the ISS, and one would expect it to be flown on future exploration class missions. A pulse oximeter, however, provides only a small subset of the information available from a full NIRS measurement. In particular, pulse oximetry can only provide oxygenation measures in arterial blood when a sufficiently strong pulse is available, whereas NIRS measurements can provide arterial measurements as well as venous and whole-tissue measurements, and does not require clear pulse signals (e.g., compartment syndrome, during muscle contractions, or in patients with a weak or thready pulse). A NIRS-based imager can further provide spatial information about tissue oxygenation or perfusion. This can help, for example, with: (1) assessing cerebral hemodynamics for conditions such as visual impairment/intracranial pressure (VIIP), including tissue oxygenation in different tissue layers (e.g., scalp versus cerebral oxygenation, or skin versus fat versus deeper muscle layers), (2) identifying the location or evaluating the size of an internal hemorrhage, or (3) assessing the relative conditioning status of different but adjacent muscle groups. Moreover, when deploying a sufficient number of near-infrared wavelengths and source/detector locations, one can further measure water content (e.g., edema), and correct measurements of deeper tissue layers for skin color, fat layers, and dynamic changes in systemic physiology (cardiac, respiratory, and other vasomotor interference). These capabilities of NIRS over standard pulse oximetry are not currently available in spaceflight but could be provided by NINscan M. The oxygenation and perfusion measures just described can also be enhanced by various auxiliary measurements. For example, electrocardiography (ECG) can be combined with systemic NIRS measurements to help estimate cardiac output. Electromyography (EMG) can be combined with muscle oxygenation measures to better understand muscle endurance and conditioning. Accelerometry and temperature measures can help identify and compensate for environmental influences on NIRS measurements. Our goal with NINscan M is to provide not only shallow- and deep-tissue NIRS imaging capabilities, but also the ability to record various auxiliary measures—each useful in their own right—to enhance NIRS assessment capabilities. NIRS and auxiliary functions are being provided modularly, so that missions with different requirements need only pack and deploy the necessary components. Importantly, the system will integrate with the SmartMED platform to minimize astronaut time and training burdens arising from data collection and management.

Earth Benefits: The same capabilities that are useful for exploration spaceflight are also relevant for Earth-based applications. For example, continuous non-invasive brain monitoring for cerebral hemorrhage is a key and unmet need following neurosurgery, stroke, and traumatic brain injury. Non-invasive monitoring of brain motion within the skull is another unmet need both in research and prevention of traumatic brain injury. Real-time muscle oxygenation imaging can be used to optimize elite athlete training as well as enhance rehabilitation protocols. And the entire field of human neuroscience is largely constrained to using large machines for brain function monitoring that require the subject to remain as still as possible. NINscan-M provides the ability to monitor brain function during people's daily activities, opening up entirely new domains of inquiry. The NINscan-M device is expected to be useful in these and other contexts.

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