Research

Medical Technology

  • Current Research
  • Previous Research

Overview

Noninvasive Measurement of Blood and Tissue Chemistry (2004-2007)

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

Organization:
University of Massachusetts Medical School

Diagnosing and monitoring medical problems during long-duration flights will be critical to mission success, but these tasks must be carried out by astronauts with limited medical training and equipment. Dr. Babs R. Soller has developed methods to use near infrared spectroscopy (NIRS) to noninvasively measure muscle oxygen levels, pH and red blood cell count. This technique can provide noninvasive physiologic monitoring in support of multiple NASA needs. Her group is developing and testing a small, lightweight medical monitor which utilizes NIRS to measure these important metabolic parameters. One use will be the assessment of fitness before, during and after spaceflight. An additional use will be to help diagnose and prevent complications from traumatic injury. The system will be directly applicable to Earth for military and civilian personnel treating mass casualties, and can also be used in hospitals, ambulances and helicopters.

NASA Taskbook Entry

Technical Summary

Trauma and acute medical problems, along with the loss of skeletal muscle mass, strength and endurance, are some of the most serious risks facing astronauts during long-duration spaceflight. The measurement of two metabolic parameters, muscle pH and oxygen, can be applied in both areas. This project examines the hypothesis that near infrared spectroscopy (NIRS) is a platform technology that can provide noninvasive physiologic monitoring in support of multiple NASA needs.

The immediate goal is to produce, validate and deliver to NASA Johnson Space Center a small, lightweight medical monitor, which utilizes NIRS to measure important metabolic parameters. Requisite precision and accuracy will be demonstrated for both male and female subjects of any ethnic origin. The device will perform equally well on the forearm and the thigh, despite gender and weight-related differences in fat thickness.

Specific Aims

  1. Develop calibration procedures for a modified NIRS sensor to measure deep muscle metabolic parameters (tissue pH and oxygen);
  2. Validate sensor in exercise protocol and deliver systems to JSC;
  3. Determine values for tissue pH and oxygen that can be used by a smart medical system to indicate shock and assist in guiding treatment; and
  4. Evaluate hardware for flight requirements and develop plans to produce a flight-ready instrumentation.

During Year 3 of this project, we continued to validate and improve the robustness of our calibration equations for noninvasively measuring muscle pH and PO2. We also developed a new methodology for determining muscle oxygen saturation. We completed the development of a system for measuring through thicker fat layers on the thigh and delivered the system to JSC. As part of this system, we developed a mechanical fixture for stabilizing the sensor on the leg and showed that measurements were immune to motion artifacts. A pilot study of 10 subjects was completed at JSC demonstrating performance of our system during a VO2max cycle ergometry test. Using data from our system, we demonstrated the capability to accurately determine the anaerobic threshold noninvasively from our pH measurements and demonstrated the feasibility of noninvasively determining oxygen uptake using only NIRS-determined parameters.

The other intended application of the system will be as a smart medical system for the assessment and treatment of critically ill and injured crew. We have begun a study in the University of Massachusetts Medical School Emergency Department of patients with severe sepsis. We demonstrated that our muscle oxygen saturation measurement was highly correlated with blood lactate, indicating the severity of microvascular impairment and the response of the patient to therapy. We also demonstrated good agreement of our noninvasive pH measurement with pH values determined from venous blood.

We have initiated discussions with three potential commercial partners who have expressed an interest in working with us to develop miniature hardware, which will be more suitable for spaceflight. We have also begun discussions with personnel at NASA Glenn Research Center about assistance in developing hardware, which is designed to be flight certified.

The NIRS noninvasive metabolic monitor is expected to have many applications for NASA. The system will have additional use on Earth for military and civilian personnel treating critically ill and injured patients. It can also be used in the hospital, ambulances and helicopters. As part of a smart medical system, advanced medical assessment and monitoring may become available to physicians in remote and rural areas, who may not have access to specialist expertise.

Earth Applications

This work will have direct Earth-based application. The prototype monitors we have developed 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 distinguishing between hemorrhagic and septic shock and helping to assess the effectiveness of sepsis treatments. The direct muscle 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. There is also general medical application for the diagnosis of anemia and if small and inexpensive enough, screening world-wide for malnutrition. There is also a possible application for the diagnosis of diabetic foot ulcers. A smaller version of this monitor could find use in the training of elite and weekend athletes.

This project's funding ended in 2007