Overview

The Venus prototype is a noninvasive, needle-free system that uses light to measure tissue oxygen and pH. Consisting of a sensor (shown on the arm) and a monitor, Venus will soon be a real-time alternative to the painful use of needles to draw blood and the cumbersome equipment used to determine metabolic rate. Venus is being developed by Dr. Babs Soller for the NSBRI for use by NASA astronauts. It will also have many applications for health care and athletic training on Earth. Courtesy of Babs Soller, Ph.D. Click here for larger image.

Noninvasive Biosensor Algorithms for Continuous Metabolic Rate Determination

The Venus prototype is a noninvasive, needle-free system that uses light to measure tissue oxygen and pH. Consisting of a sensor (shown on the thigh) and a wearable monitor, Venus will soon be a real-time alternative to the painful use of needles to draw blood and the cumbersome equipment used to determine metabolic rate. Venus is being developed by Dr. Babs Soller for the NSBRI for use by NASA astronauts. It will also have many applications for health care and athletic training on Earth. Photo by Luigi Piarulli. Click here for larger image.

Principal Investigator:
Babs R. Soller, Ph.D.

Organization:
Reflectance Medical Inc.

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. Through her previous NSBRI project, Dr. Babs R. Soller and colleagues developed a biosensor that uses near infrared spectroscopy (NIRS) to noninvasively measure blood and tissue chemistry important in assessing metabolism.

With this project, Dr. Soller is working on new algorithms for the biosensor, enabling it to accurately and continuously assess metabolic rate. Dr. Soller’s team is also working on a smaller version of the sensor so that it will fit comfortably within the spacesuit. The sensor and algorithms are intended for use during the development of new spacesuits and ultimately when astronauts undertake future exploration missions. Earth applications include noninvasive, real-time assessment of metabolic rate as part of a fitness or weight loss program.

NASA Taskbook Entry

Technical Summary

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).

Specific Aims

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.
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 made significant progress in developing the components of the algorithm to calculate VO₂ from NIR spectra. We completed the initial algorithm to estimate stroke volume and made advancements in improving the accuracy of our hematocrit calculation. We 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, which is 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 two groups.

With synergistic funds from the U.S. Army Medical Research Command, we continued to develop the solid state sensor and software to support it. The first systems were delivered to NASA Johnson Space Center for testing in the Exercise Physiology Lab. According to the users, hardware and software usability was greatly improved over the fiber optic system.

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 U.S. Food and Drug Administration in early 2011.

Earth Applications

This work will have direct Earth-based applications. 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 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, 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 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 the Telemedicine and Advanced Technology Research Center. We have received institutional review board approval and traveled to Bangkok to train the research nurses. Patient enrollment will begin in September 2010.

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

This project's funding ended in 2012