Paper Session II-B - Optical Diagnostics: Reagentless Chemistry for Extended Space Flights

Maintaining the health and safety of the crews of spacecraft remain the highest priorities. Health monitoring requires at least two overlapping activities: (I) frequent or continuous monitoring of bodily functions to determine normalcy or deviation from normalcy, and (2) specific diagnosis and treatment of diseases. Thus, with a broad mandate and limited resources, the spacecraft must provide the diagnostic capabilities for quickly and accurately diagnosing a wide range of diseases. Optical devices, though still in the early developmental stages, diagnose diseases by analyzing and quantitating the spectra of metabolites and other substances non-invasively and without using chemical reagents. Once commercially available, optical devices will replace many clinical 1es1s that use chemical reagents for diagnostics. INTRODUCTION Ensuring the health of crews is essential for the successful completion of the various tasks of missions. Although crews are thoroughly examined and treated for their diseases prior 10 missions, they are subjected to various stresses during flights that can increase their susceptibilities to diseases. For extended missions, the spacecraft must stock an inventory of different diagnostic kits (each containing its own specific reagents) and medications in order to test for and treat a broad range of diseases accurately and quickly. The diagnostic kits and devices must conform to the constraints imposed by size, weight, and power consumption. After their use, the spacecraft must safely store or degrade the chemical reagents, blood and other body fluids, and non-reusable devices. In contrast, optical devices perform diagnoses non-invasively, do not require samples of blood or body fluids, can operate almost continuously, and use no reagents or supplies. Optical devices offer advantages for extended missions not provided by test kits that use chemical reagents. We are developing an optical device using near-infrared spectroscopy for monitoring blood chemistry (glucose) non-invasively (without drawing blood). This technique, sometimes called "reagentless chemistry" involves identification and quantitation of the spectra of different chemicals in the blood. When fully developed, the patient will illuminate a finger (Fig. 8), ear lobe or other optically translucent area and sensor detects the spectral signals on the other side. Using signal processing techniques, background noise iS removed and spectral signal are quantitated (Ham. 1994; Ham et al., 1994). For our research on blood glucose, we felt that the non-invasive device had to meet at a minimum of three requirements: (1) measures the substance in the blood directly using a safe, lowintensity, near infrared source; (2) determines concentrations of blood substances using an artificial neural network and signal processing techniques, and (3) measures the substance in the blood independently of both skin pigmentation and the finger site where the light impinges. METHODOLOGY AND PRELIMINA RY RESULTS The Data Sets and the Baseline Corrections A very comprehensive data set, consisting of 1251 near infrared (NIR) spectra of human blood serum, has been generated by Mi les, Inc. (NonInvasive and In-Licensing Diabetes Business Unit).