The objectives of this test were to determine whether Non-Invasive Near Infrared Spectroscopy (NIRS) could be used noninvasively and unobtrusively to measure oxygen consumption and pH (as a correlate to lactic acid concentration) during cycle ergometry exercise, both before and after bed rest.
This experiment was designed to develop novel algorithms for existing near infrared spectroscopy (NIRS) platform for real-time assessment of metabolic rate (measured as the rate of oxygen consumption, VO2) and muscle temperature. This capability was intended to be incorporated into biosensors which were part of a smart system to advise astronauts regarding their usage of consumables during lunar surface activities.
The following specific aims were proposed:
1. Develop and validate algorithms to accurately calculate VO2 from NIR spectra collected from muscle
2. Develop and validate algorithms to simultaneously calculate muscle temperature
3. Support incorporation of the sensor algorithms into the EVA suit testing program, where practical.
The feasibility was demonstrated by determining VO2 with the Fick equation and data that was collected solely through a NIRS system. The accuracy of this technique was currently limited at high exercise intensities, primarily due to inaccuracies in the stroke volume estimate. Improvements were made on the accuracy of the NIRS measurements used to calculate oxygen content. These improvements were tested with the data collected from the bed rest subjects, as well as the data collected from a hypovolemia study, which looked at the effects of plasma volume changes alone on these measurements.
Collaboration efforts, supported by non-NASA funds, was initiated to develop a solid-state, low profile spectroscopic sensor which had the potential to provide a prototype unit with appropriate characteristics which was used for ground testing within the extra-vehicular activity (EVA) suit.
The proposed biosensor system had built-in redundancy through easy application to both limbs. The biosensor also provided system redundancy in the measurement of heart rate and temperature to further ensure astronaut safety. The proposed technology was expected to result in wearable sensors that terrestrial doctors and their patients could use to track and optimize exercise in the management of both health and fitness, as well as during related applications for the care of critically ill patients.