The International Space Station Health Maintenance Facility was designed to provide medical care to crewmembers for up to 10 days. An integral part of the Health Maintenance Facility is the capability to supply intravenous (IV) fluids to sustain an ill or injured crewmember. In health care facilities on Earth, IV solutions are normally stored in large quantities. However, due to weight and volume constraints, an adequate supply of the required solutions cannot be carried on board the space station. By formulating medical fluids on board from concentrates and space station water as needed, the Fluid Therapy System (FTS) was designed to eliminate weight and volume as constraints.
Evaluation of the FTS equipment focused on the needs of the space station. A one-bed hospital to support a four-man crew during the Permanently Manned-Tended phase was developed. During this phase, medical operations would be responsible for treating minor ailments, but could also intervene in the case of an emergency. During these emergencies, the crewmembers might need IV fluids rapidly and possibly for several days until they could be stabilized and returned to Earth. The FTS represents one aspect of the emergency medical care required.
The FTS evaluation consisted of two functional objectives and an in-flight demonstration of IV administration of fluids. The first objective was to make sterile water and IV solutions on board the Shuttle. If IV fluids are to be produced on the space station, successful sterilization of water and reconstitution of IV solutions must be achieved. The second objective was to repeat the FTS infusion pump verification, which had been performed initially on Spacelab Life Sciences 1 (SLS-1). Finally, the technique of starting an IV in microgravity was demonstrated. The IV technique required modifications in microgravity, such as the use of restraints for equipment and crewmembers involved.
The FTS experiment hardware consisted of nine major components: Source Water Container (SWC), Sterile Water for Injection System (SWIS), Intravenous Reconstituting Device (IRD), Large Volume Parenteral (LVP) bags, Intravenous Fluid Infusion Pump (IV pump), Payload General Support Computer (PGSC), Fluid Administration Set, Sample Containment Device, and Flight Infusion System Test (FIST) equipment.
The SWC was a steel tank that contained tap water from Kennedy Space Center (KSC). For the first objective, water from the SWC was passed through the SWIS, a cartridge designed to purify water by passing it across various beds of activated carbons and deionizing resin. In addition, the water was passed through an ultra-filter and stored in LVP bags. When IV fluids were to be made, the IRD was connected between the output line of the SWIS and the LVP bag. The IRD was a flow-through pouch that contained liquid concentrates of the solutions to be mixed with sterile water, which in turn would reconstitute single units of IV fluids. The IV fluids to be made were either 5% dextrose in water or normal saline (0.9% sodium chloride).
The second objective required the use of an IV pump with two pumping channels that allowed for simultaneous infusion of two separate solutions at different rates. This feature also provided redundancy in the event either channel failed. The IV pump delivered fluid solutions via the Fluid Administration Set to the Sample Containment Device, a series of one-liter bags used to hold the pumped solution. After the second and third bags were produced, FTS infusion pump mechanics and operations were reverified. One bag of normal saline and one bag of 5% dextrose in water were attached to the IV pump. The crewmember monitored the filling of the LVP bags during sterilization and reconstitution of IV fluids, while the PGSC controlled the IV pump. The PGSC would also signal the crewmember to change the flow rates. The flow rates tested were 25, 80, 125, and 300 mL/h, and each test lasted 30 minutes. The PGSC controlled starts and stops, and noted pump alarms and pump output data.
The last part of the system evaluation was IV infusion in continuous microgravity. A mannequin arm was used to practice the insertion of an IV line. The mannequin arm was designed with venous channels to simulate a patient's arm. The IV pump operated at several flow rates and intentional failures were produced to determine effective methods for coping with failures. Simultaneous ground testing was completed at KSC to provide comparable 1-G samples, as well as provide the capability of troubleshooting any malfunctions that may have occurred during flight.
Both the flight and ground samples were collected at the landing site. They were placed on ice and immediately returned to the Johnson Space Center (JSC) for analysis. The JSC Biomedical Operations and Research Branch performed the necessary analysis and tests on the samples to determine if the experiment was successful in producing sterile solutions that contained the correct amount of electrolytes. The temperature of the stored water in the SWC and the LVP bags was monitored continuously to assist with the postflight analysis of the samples.
Water sterilization and IV solution production were completed with eight 1-liter bags of either sterile water, 5% dextrose in water or normal saline being produced. During the filling, a significant development of micro-sized bubbles was noted. The production of these bubbles was possibly due to incomplete de-airing of the ultra-filter or was the result of fluid being forced through narrow connection openings causing cavitation (the formation of low pressure bubbles in liquid). Intravenous pump verification and performance was normal.
Analysis of the baseline water samples taken from KSC revealed that the tap water contained low concentrations of endotoxins and common waterborne bacteria. Inflight water samples collected directly from the SWC contained low concentrations of endotoxins and a low bacterial count. Water taken from a ground-based water container had an endotoxin concentration of nearly twice that found in the flight tank and increased bacterial count. Inflight and ground samples collected after the water purification process did not contain bacterial growth.
Chemical analysis of the samples indicated that the percent concentration of 5% dextrose in water ranged from 4.8% in 1030 mL of fluid to 5.5% in 907 mL. For normal saline (0.9% sodium chloride), concentrations ranged from 0.86% in 1074 mL of fluid to 1.04% in 925 mL.
The concentration of trace metals, anions, and cations were within normal limits for all sample types based on United States Pharmacopeia XXI standards. Intravenous pump flow rate testing suggested that a zero-pressure head induces a 2-4% negative error from the set rates. When the in-line filter is added to the fluid administration set (FAS) at a standard pressure head of 20 inches, the resistance associated with the in-line filter resulted in a 1-3% negative error from the set rate. When these two factors are combined, the total error ranges from 3-9%.
In-flight results showed the lowest error was when running Channel B at a set flow rate of 80 mL/h (5.3% error); the highest was noted on Channel A when running at a set rate of 125 mL/h (9.9% error). In results from the testing being performed on the ground, the lowest error was noted on Channel A when running at a set rate of 80 mL/h (5.8% error) and the highest error was on Channel B when running at a set rate of 300 mL/h (7.8% error).
In conclusion, the system was able to produce the three types of solutions required for medical care. Reverification of the FTS infusion pump system indicated that the hardware performed consistently within the experiment goal of less than 10% error at all flow rates.
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