Longer duration missions as outlined in the Vision for Space Exploration increase the likelihood of requiring intravenous (IV) fluids to treat a medical emergency. In some instances, as in the case of severe burns, proper medical treatment may require up to 32 liters of intravenous fluid weighing over 32 kg (70.5 lb), see reference 1. Because a system to generate medical grade water and mix it with powders or concentrates would reduce the mass requirements for IV fluids, in fiscal year 2006 the NASA Glenn Research Center analyzed several potential methods for mixing powders or concentrates with sterile water to produce IV fluid. The researchers found that a standard magnetic stirrer would be highly effective, being low in mass and high in mixing efficiency. Ground experiments were performed to validate the efficiency of this mixing method. More specifically, the amount of time required to mix the fluid to concentration tolerances defined by the Food and Drug Administration (FDA) was determined, and a noninvasive optical diagnostic technique was used to quantify these mixing times.
Planar Laser-Induced Fluorescence (PLIF) is an optical technique in which a laser source is used to form a thin sheet of light that traverses a flow field of interest. If the laser wavelength is resonant with the optical shift of a species present in the flow, a portion of the incident light will be absorbed and emitted, at a longer wavelength, by that species at each point within the illumination plane. When the emitted light, or fluorescence, is imaged, the amount of light detected by a pixel of the camera depends on the concentration of the species of interest within the corresponding measurement volume and the local flow field conditions (i.e., temperature, pressure). The PLIF experimental setup at Glenn included a continuous-wave, 200-mW, 532-nm Nd:YAG laser that was passed through a planoconvex lens to create a divergent laser sheet. An optically flat mirror deflected the laser sheet into an acrylic test section, which approximated a 1-liter commercial IV bag. A 12-bit monochromatic 1024- by 768-pixel camera with a 35-mm lens was placed perpendicular to the laser sheet and focused on a cross section of interest. PLIF image sequences were acquired of a salt solution containing fluorescent dye (Rhodamine 6G) mixed with distilled water to mimic the production of a standard IV fluid: normal saline. The experimental setup and a sample image are shown in the left and right photographs, respectively.
Left: PLIF experimental setup. Right: An example of a PLIF image (enhanced for publication).
A histogram analysis of the normalized pixel intensity for the series of images was used to plot the peak intensity over time (see the following graph on the left). A fully mixed solution was indicated when the mean intensity curve formed an asymptote to the normalized final intensity. Mixing times for a 95-percent homogenous solution were plotted for stir bars of various sizes (see the following graph on the right). The plot indicates that these solutions can mix within a few seconds, particularly with the longer stir bars. Analysis is under way to determine the effect of gravity on the mixing time. If convective mixing is similar in microgravity, this mixing method would be able to produce IV fluids in emergency situations.
Left: Normalized histogram peak intensity over time. Right: Time versus revolutions per minute required to achieve a 95-percent homogenous solution with various stir bar sizes.
Glenn contacts:
Karen L. Barlow, 216-433-3543, Karen.L.Barlow@nasa.gov
Charles E. Niederhaus, 216-433-5461, Charles.E.Niederhaus@nasa.gov
Authors:
Karen L. Barlow and Dr. Charles E. Niederhaus
Headquarters program office:
Exploration Systems Mission Directorate
Programs/projects:
Exploration Medical Capabilities
Last updated: August 30, 2007
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Gynelle.C.Steele@nasa.gov, 216-433-8258
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216-433-8258
Point of contact for NASA Glenn's Research & Technology reports:
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216-433-2912
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