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Noninvasive Biosensor Algorithms for Continuous Metabolic Rate Determination

Completed TRL 6 (started at 4, targeting 6)

Description

NASA is designing new spacesuits to meet the needs of future space exploration. Real-time measurement of metabolic rate during astronaut activity is a key function of the biosensor suite which is planned for the new spacesuit. This project is developing novel near infrared spectroscopic (NIRS) algorithms and sensors for real-time assessment of metabolic rate (measured as the rate of oxygen consumption, VO2). This capability is intended to be incorporated into a smart system advising astronauts on their use of consumables during extravehicular activity (EVA). The specific aims of this project include the development of algorithms to calculate VO2 from NIRS spectra and validation of the algorithms during exercise in two different ground-based protocols which simulate plasma volume reduction during spaceflight. An additional aim of this project is to support the EVA suit testing program by developing small, lightweight and robust sensors which can be used within the spacesuit to evaluate metabolic cost of the suit itself, on individual muscles.

Over the last year we have made significant progress in developing the components of the algorithm to calculate VO2 from NIR spectra. We have completed the initial algorithm to estimate stroke volume and made advancements in improving the accuracy of our hematocrit calculation. We have further optimized our measurement of muscle oxygen saturation and demonstrated its high degree of accuracy under a number of potential confounding factors. Most important for space application, we demonstrated accuracy under conditions that simulate factors that occur during fluid shifts, i.e., variation in blood and water fraction, as well as changes in blood vessel size.

We completed data collection for a study of pharmacologically induced hypovolemia, one of the validation studies we will use to assess performance of our VO2 algorithms. Initial data analysis showed that noninvasively determined NIRS parameters, muscle oxygen saturation, and hydrogen ion threshold were not different between the hypovolemia and normovolemia exercise sessions. This result is in agreement with the finding that lactate at peak exercise was not different between the 2 groups.

With synergistic funds from the US Army Medical Research Command we continued to develop the solid state sensor and software to support it. The first systems were delivered to Johnson Space Center (JSC) for testing in the Exercise Physiology lab. Hardware and software usability was greatly improved over the fiber optic system according to the users.

This project has produced a prototype wearable sensor that terrestrial doctors and their patients can use to track and optimize exercise in the management of health and fitness, as well as during related applications in the care of critically ill patients. A company has been formed to commercialize the sensor. The company is on target to submit a 510(k) application to the FDA (Food and Drug Administration) in early 2011.

Benefits

This work will have direct Earth-based application. The fitness and exercise applications we are developing can be used to assist in the training and evaluation of elite and recreational athletes. This direct application of interest to NASA for assessing fitness in space may be useful to assess success of physical therapy in rehabilitating patients with muscle injury or atrophy.

The sensor, which also is of tremendous interest to the Army, will have application in emergency response vehicles, emergency rooms, and hospitals. Pre-hospital applications include assessing the severity of shock and triaging multiple casualties, as well as providing a sensor for a smart medical system to guide resuscitation from hemorrhage. In the Intensive Care Unit (ICU) we expect that this monitor will find application in helping provide early identification of patients with hemodynamic instability before they go into shock.

We are partnering with the Armed Forces Research Institute of Medical Science (AFRIMS) in Bangkok, Thailand to study the application of our sensor for the early identification of shock in children with Dengue hemorrhagic fever. This study is funded by Telemedicine & Advanced Technology Research Center (TATRC). We have received IRB (institutional review board) approval and traveled to Bangkok to train the research nurses. Patient enrollment will begin in September.

The company formed to commercialize the sensor has received a Phase II STTR (Small Business Technology Transfer) grant from the US Army. This effort is focused on obtaining FDA clearance through the 510(k) mechanism, to market the sensor in the US. The company is on track to submit this application in early 2011.

Details

Technology areaHuman Health, Life Support, and Habitation Systems > Human Health and Performance > Contactless and Wearable Human Health and Performance Monitoring
ProgramHuman Research Program (HRP)
Lead organizationNational Space Biomedical Research Institute, Houston, TX
Start date2007-10-01
End date2010-09-30

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This is early/mid-stage (TRL 6) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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