The overall goal of Dr. Steinke's Phase II is to develop a spectrophotometric instrument capable of measuring eight quantities directly in a sample of undiluted whole blood. These include: THb (total hemoglobin concentration); percent Hb02 (percent oxyhemoglobin saturation); percent HbCO (percent carboxyhemoglobin saturation); percent Hi (percent methemoglobin saturation; also known as hemiglobin); percent Hb (percent deoxyhemoglobin saturation); percent SHb (percent sulfhemoglobin saturation); [02] (Hb02 concentration, which approximates oxygen content); and [Bill} (bilirubin concentration). In Phase I, Dr. Steinke developed a prototype spectrophotometer, based on a computer-controlled miniature monochromator, which made measurements in whole blood in spite of blood's well known light scattering properties. To measure the five hemoglobin species and bilirubin requires 6 carefully chosen measuring wavelengths and a 7th wavelength to correct for light scattering; THb and [02] are computed variables not requiring specific wavelengths. The principal aim of Phase II is to evaluate four sources of the 7 monochromatic wavelengths needed for the measurements. The purpose of doing so is to increase the ruggedness of the final design, prove the stability and wavelength stability, and achieve a significant reduction in manufacturing costs. He will fabricate and test four different light sources: (1) Fixed-diffraction grating - multiple light source array. In this light source, individual beams will be focused through seven adjacent input slits onto a single grating. Light enters only one slit at a time because only one lamp at a time will be illuminated. The entrance slits are carefully machined sot that they select each of the 7 desired wavelengths. (2) Hybrid circuit LED array and filter wheel. This light source will consist of an array of seven light emitting diodes(LED's), one for each of the required analytical wavelengths. The emission of each LED will pass through a narrow-band interference filter mounted on a filter wheel. During each measurement cycle, the desired wavelengths will be selected sequentially by rotating the appropriate filter into position in front of the sample and simultaneously energizing the corresponding LED. (3) Special cam monochromator. This light source will consist of a miniature monochromator with a special cam shaft. The special cam will be used to rotate a diffraction grafting, and will have one distinct radius for each of the seven analytical wavelengths. (4) Samarium-neon hollow cathode lamp. Samarium and neon together provide emission wavelengths very close to each of the seven optimal wavelengths to be utilized in Dr. Steinke's device. Light from this source will be sequentially passed through seven filters, each of which will eliminate all wavelengths except the one assigned to that filter.
