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All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

The Value of Biomedical Simulation Environments to Future Human Space Flight Missions

Mars and NEO missions will expose astronaut to extended durations of reduced reduced gravity, isolation and higher radiation. These new operation conditions pose health risks that are not well understood and perhaps unanticipated. Advanced computational simulation environments can beneficially augment research to predict, assess and mitigate potential hazards to astronaut health. The NASA Digital Astronaut Project (DAP), within the NASA Human Research Program, strives to achieve this goal.

Mulugeta,Lealem↗
NASA NTRS2017

Cancer Risk in Astronauts: A Constellation of Uncommon Consequences

Excess cancers resulting from external radiation exposures have been noted since the early 1950s, when a rise in leukemia rates was first reported in young atomic bomb survivors [1]. Further studies in atomic bomb survivors, cancer patients treated with radiotherapy, and nuclear power plant workers have confirmed that radiation exposure increases the risk of not only leukemia, but also a wide array of solid cancers [2,3]. NASA has long been aware of this risk and limits astronauts' risk of exposure-induced death (REID) from cancer by specifying permissible mission durations (PMD) for astronauts on an individual basis. While cancer is present among astronauts, current data does not suggest any excess of known radiation-induced cancers relative to a comparable population of U.S. adults; however, very uncommon cancers have been diagnosed in astronauts including nasopharyngeal cancer, lymphoma of the brain, and acral myxoinflammatory fibroblastic sarcoma. In order to study cancer risk in astronauts, a number of obstacles must be overcome. Firstly, several factors make the astronaut cohort considerably different from the cohorts that have previously been studied for effects resulting from radiation exposure. The high rate of accidents and the much healthier lifestyle of astronauts compared to the U.S. population make finding a suitable comparison population a problematic task. Space radiation differs substantially from terrestrial radiation exposures studied in the past; therefore, analyses of galactic cosmic radiation (GCR) in animal models must be conducted and correctly applied to the human experience. Secondly, a large enough population of exposed astronauts must exist in order to obtain the data necessary to see any potential statistically significant differences between the astronauts and the control population. Thirdly, confounders and effect modifiers, such as smoking, diet, and other space stressors, must be correctly identified and controlled for in those analyses. In order to begin work assessing the astronaut population, the earliest groups of astronauts (selection groups 1-7) provide a unique model. These astronauts were relatively homogenous, white males whose lifestyle characteristics were similar to an average U.S. citizen of the same birth cohort. This work reviews radiation exposure levels, age, and causes of mortality among these early NASA astronauts and discusses the benefits and limitations of assessing such a cohort for radiation-induced cancer risk.

Milder, Caitlin M.↗
NASA NTRS2001

Development of a Neutron Spectrometer to Assess Biological Radiation Damage Behind Spacecraft Materials

Astronauts who spend months and years traveling long distances in spacecraft and working on other planets will be subjected to high energy radiation of galactic and solar origin without the protection of the Earth's thick (one writer has called it buff) atmosphere and magnetic field. The lack of natural protection will allow high energy cosmic ray particles and solar protons to crash directly into relatively thin spacecraft walls and planetary atmospheres producing energetic secondary particles in these collisions. A substantial fraction of these secondaries will be neutrons that carry no electric charge and, consequently, are difficult to detect. At sea level on Earth the remaining neutrons are the result of many generations (approximately 10) of collisions, have very low energies (scientists call them thermal neutrons), and do not penetrate deeply into the human body. They do contribute to the natural background radiation seen by humans on Earth, but much of the dose is only at the surface or skin of the body. In the International Space Station or on the surface of Mars, the secondary neutrons will be the result of only one or two generations of interaction due to the thinner (about a factor of 20 compared to the Earth's atmosphere) walls or atmosphere, have considerably more energy and penetrate deeply into the human body. In addition, neutrons are substantially moderated by hydrogenous material such as water. A significant fraction of the water exists in the astronaut's body. Therefore, the neutron can not only penetrate more deeply into the body, but also be stopped there and deposit all or most of its radiation dose in organs such as the liver, spleen, kidney, etc. We hypothesize that the risk of serious cancers will be increased for the exposed humans. The portable, real time neutron spectrometer being developed by our team will monitor the environment inside spacecraft structures and on planetary surfaces. Activities supported by this grant will evaluate the neutron environment inside several candidate spacecraft materials at accelerator facilities. These experiments will enable engineers to choose the structure materials that minimize the production of secondary neutrons. With the information that the neutron energy spectrometer produces, scientists and doctors will be able to assess the increased risk of cancer and develop countermeasures. The instrument itself will include an alarm system to warn astronauts when high radiation fluxes are occurring so that they can seek shelter immediately.

Maurer, R. H.↗
NASA NTRS2021

Comparison of Health and Performance Risk for Accelerated Mars Mission Scenarios

This document details the results for a quantitative estimate of the difference in human health and performance risk that crews would face for two hypothetical variations on Mars mission scenarios: an Accelerated Mars Mission (AMM) and a Standard Mars Mission(SMM).NASA goals for Mars mission concepts, duration, and tasks have varied over the years. While neither of the cases considered here are likely to accurately represent the initial mission to Mars, the exercise of evaluating significant differences in mission duration from an astronaut health perspective can provide bounding insight to the level of risk that is likely to be encountered in an eventual Mars mission. Medical Probabilistic Risk Assessment using the Integrated Medical Model (IMM)(1–3)and the NASA Space Radiation Cancer Risk Model (NSCR)(4,5) are used here to help mission planners gain the best insight currently available into the expected magnitude of impacts to astronaut health when undertaking a Mars mission. These impacts occur both in-mission as well as in the long-term health of the astronauts post-mission. These evaluations are currently the best available modeling estimates to characterize and bound the health risks in a proposed mission domain where humans have no experience.

Erik Antonsen↗
NASA NTRS1975

The Apollo 17 pocket mouse experiment (Biocore)

Results are presented of the Biocore experiment which attempted to assess the degree to which exposure to cosmic ray particle radiation might present a risk to astronauts. Pocket mice, with plastic dosimeters implanted beneath the scalp were flown in a sealed canister. The objective was to determine whether microscopically visible lesions attributable to particle radiation, could be found in brain, eye, and other tissues in these animals. The need for further study is demonstrated.

Webb Haymaker↗
NASA NTRS2007

Space Radiation and its Associated Health Consequences

During space travel, astronauts are exposed to energetic particles of a complex composition and energy distribution. For the same amount of absorbed dose, these particles can be much more effective than X- or gamma rays in the induction of biological effects, including cell inactivation, genetic mutations, cataracts, and cancer induction. Several of the biological consequences of space radiation exposure have already been observed in astronauts. This presentation will introduce the space radiation environment and discuss its associated health risks. Accurate assessment of the radiation risks and development of respective countermeasures are essential for the success of future exploration missions to the Moon and Mars.

Wu, Honglu↗
NASA NTRS2014

Understanding the Effects of Long-duration Space Flight on Astronant Functional Task Performance

Space flight is known to cause alterations in multiple physiological systems including changes in sensorimotor, cardiovascular, and neuromuscular systems. These physiological changes cause balance, gait and visual disturbances, cardiovascular deconditioning, and loss of muscle mass and strength. These changes may affect a crewmember's ability to perform critical mission tasks immediately after landing on a planetary surface. To understand how changes in physiological function affect functional performance, an interdisciplinary pre- and postflight testing regimen, Functional Task Test (FTT), was developed to systematically evaluate both astronaut functional performance and related physiological changes. Ultimately this information will be used to assess performance risks and inform the design of countermeasures for exploration class missions. We are currently conducting the FTT study on International Space Station (ISS) crewmembers before and after 6-month expeditions. Additionally, in a corresponding study we are using the FTT protocol on subjects before and after 70 days of 6deg head-down bed-rest as an analog for space flight. Bed-rest provides the opportunity for us to investigate the role of prolonged axial body unloading in isolation from the other physiological effects produced by exposure to the microgravity environment of space flight. Therefore, the bed rest analog allows us to investigate the impact of body unloading on both functional tasks and on the underlying physiological factors that lead to decrement in performance and then compare them with the results obtained in our space flight study. Functional tests included ladder climbing, hatch opening, jump down, manual manipulation of objects and tool use, seat egress and obstacle avoidance, recovery from a fall and object translation tasks. Physiological measures included assessments of postural and gait control, dynamic visual acuity, fine motor control, plasma volume, heart rate, blood pressure, orthostatic intolerance, upper- and lower-body muscle strength, power, endurance, control, and neuromuscular drive. ISS crewmembers were tested three times before flight, and on 1, 6, and 30 days after landing. Bed-rest subjects were tested three times before bed-rest and immediately after getting up from bed-rest as well as 1, 6, and 12 days after reambulation.

Bloomberg, Jacob J.↗
NASA NTRS2019

Comparison of Risk from Orbital Debris and Meteoroid Environment Models on the Extravehicular Mobility Unit (EMU)

A well-known hazard associated with exposure to the space environment is the risk of failure from an impact from a meteoroid and orbital debris (MMOD) particle. An extravehicular mobility unit (EMU) “spacesuit” impact during a US extravehicular activity (EVA) is of great concern as a large leak could prevent an astronaut from safely reaching the airlock in time resulting in a loss of life. A risk assessment is provided to the EVA office at the Johnson Space Center (JSC) by the Hypervelocity Impact Technology (HVIT) group prior to certification of readiness for each US EVA. Need to understand the effect of updated meteoroid and orbital debris environment models to EMU risk.

Hoffman, Kevin↗
NASA NTRS2010

Space Toxicology: Human Health during Space Operations

Space Toxicology is a unique and targeted discipline for spaceflight, space habitation and occupation of celestial bodies including planets, moons and asteroids. Astronaut explorers face distinctive health challenges and limited resources for rescue and medical care during space operation. A central goal of space toxicology is to protect the health of the astronaut by assessing potential chemical exposures during spaceflight and setting safe limits that will protect the astronaut against chemical exposures, in a physiologically altered state. In order to maintain sustained occupation in space on the International Space Station (ISS), toxicological risks must be assessed and managed within the context of isolation continuous exposures, reuse of air and water, limited rescue options, and the need to use highly toxic compounds for propulsion. As we begin to explore other celestial bodies in situ toxicological risks, such as inhalation of reactive mineral dusts, must also be managed.

Khan-Mayberry, Noreen↗
NASA NTRS2014

Assessing the Risk of Crew Injury Due to Dynamic Loads During Spaceflight

Spaceflight requires tremendous amounts of energy to achieve Earth orbit and to attain escape velocity for interplanetary missions. Although the majority of the energy is managed in such a way as to limit the accelerations on the crew, several mission phases may result in crew exposure to dynamic loads. In the automotive industry, risk of serious injury can be tolerated because the probability of a crash is remote each time a person enters a vehicle, resulting in a low total risk of injury. For spaceflight, the level of acceptable injury risk must be lower to achieve a low total risk of injury because the dynamic loads are expected on each flight. To mitigate the risk of injury due to dynamic loads, the NASA Human Research Program has developed a research plan to inform the knowledge gaps and develop relevant tools for assessing injury risk. The risk of injury due to dynamic loads can be further subdivided into extrinsic and intrinsic risk factors. Extrinsic risk factors include the vehicle dynamic profile, seat and restraint design, and spacesuit design. Human tolerance to loads varies considerably depending on the direction, amplitude, and rise-time of acceleration therefore the orientation of the body to the dynamic vector is critical to determining crew risk of injury. Although a particular vehicle dynamic profile may be safe for a particular design, the seat, restraint, and suit designs can affect the risk of injury due to localized effects. In addition, characteristics intrinsic to the crewmember may also contribute to the risk of injury, such as crewmember sex, age, anthropometry, and deconditioning due to spaceflight, and each astronaut may have a different risk profile because of these factors. The purpose of the research plan is to address any knowledge gaps in the risk factors to mitigate injury risk. Methods for assessing injury risk have been well documented in other analogous industries and include human volunteer testing, human exposure to dynamic environments, post-mortem human subject (PMHS) testing, animal testing, anthropomorphic test devices (ATD), dynamic models of the human, numerical models of ATDs, and numerical models of the human. Each has inherent strengths and limitations. For example, human volunteer testing is advantageous because a population can be selected that is similar to the astronaut corps; however, because of the inherent ethical limitations, only sub-injurious conditions can be tested. PMHSs can be tested in a variety of conditions including injurious levels, but the responses are not completely analogous to living human subjects. In addition, it is exceedingly difficult to select a PMHS population that is similar to the astronaut corps. ATDs are currently widely used in the automotive industry and military because they are highly repeatable and durable. Unfortunately, because they are mechanical models of the human body, the biofidelity of the responses are limited to dynamic conditions used to validate the ATD. Numerical models of the ATD, in addition to the strengths and limitations for ATDs, are easy to use for a variety of designs before a design is fabricated, but also have additional limitations for ATDs, are easy to use for a variety of designs before a design is fabricated, but also have additional uncertainty. Dynamic models are simple and easy to use, but do not account for localized effects of the seat and suit. Finally, numerical models of the human have the potential to have the most advantages; however, the current models are not validated for the conditions expected during spaceflight. To properly assess spaceflight conditions with numerical human models, human data would be needed to optimize the model responses for those conditions. Using the appropriate assessment method with the knowledge gained for each risk factor, an appropriate approach for mitigating the risk of injury due to dynamic loads can be developed ensuring crew safety in future NASA vehicles.

Somers, J. T.↗
NASA NTRS2003

Macromolecular Expression and Function: A New Paradigm for NASA Risk Assessment

Predicting risks in humans of either acute effects such as bone loss or muscle wasting, or late effects such as cancer, is challenging. To an approximation, this is because uncertainties of exposure to stress factors or toxic agents and the uniformity of processing subsequent damage at the cellular level within a complex set of biological variables degrade the confidence of predicting pathologic outcome. A cellular biodosimeter that simultaneously reports 1) the type of damage due to that exposure, 2) the quantity of damage incurred by that exposure, and 3) the dataset used to assess risk of developing pathologic outcome caused by that exposure would therefore be useful for predicting ultimate risks faced by an individual, such as an astronaut. It is suggested that such a biodosimeter can be based upon analyses of gene-expression and protein expression whereby large datasets of cellular response to damage are obtained and analyzed for expression-profiles correlated with established end points and molecular markers predictive for risks being assessed. The usefulness of multiparametric cellular biodosimeters could be realized by quantitatively profiling these datasets using techniques of bioinformatics. Such an approach contributes to the foundation of molecular epidemiology as a new scientific discipline, and represents a new paradigm of risk assessment.

Richmond, Robert↗
NASA NTRS2000

Dose limits for astronauts

Radiation exposures to individuals in space can greatly exceed natural radiation exposure on Earth and possibly normal occupational radiation exposures as well. Consequently, procedures limiting exposures would be necessary. Limitations were proposed by the Radiobiological Advisory Panel of the National Academy of Sciences/National Research Council in 1970. This panel recommended short-term limits to avoid deterministic effects and a single career limit (of 4 Sv) based on a doubling of the cancer risk in men aged 35 to 55. Later, when risk estimates for cancer had increased and were recognized to be age and sex dependent, the NCRP, in Report No. 98 in 1989, recommended a range of career limits based on age and sex from 1 to 4 Sv. NCRP is again in the process of revising recommendations for astronaut exposure, partly because risk estimates have increased further and partly to recognize trends in limiting radiation exposure occupationally on the ground. The result of these considerations is likely to be similar short-term limits for deterministic effects but modified career limits.

Review↗
NASA NTRS2011

Space Radiation Cancer Risk Projections and Uncertainties - 2010

Uncertainties in estimating health risks from galactic cosmic rays greatly limit space mission lengths and potential risk mitigation evaluations. NASA limits astronaut exposures to a 3% risk of exposure-induced death and protects against uncertainties using an assessment of 95% confidence intervals in the projection model. Revisions to this model for lifetime cancer risks from space radiation and new estimates of model uncertainties are described here. We review models of space environments and transport code predictions of organ exposures, and characterize uncertainties in these descriptions. We summarize recent analysis of low linear energy transfer radio-epidemiology data, including revision to Japanese A-bomb survivor dosimetry, longer follow-up of exposed cohorts, and reassessments of dose and dose-rate reduction effectiveness factors. We compare these projections and uncertainties with earlier estimates. Current understanding of radiation quality effects and recent data on factors of relative biological effectiveness and particle track structure are reviewed. Recent radiobiology experiment results provide new information on solid cancer and leukemia risks from heavy ions. We also consider deviations from the paradigm of linearity at low doses of heavy ions motivated by non-targeted effects models. New findings and knowledge are used to revise the NASA risk projection model for space radiation cancer risks.

Cucinotta, Francis A.↗
NASA NTRS2012

Development of a High Fidelity Dynamic Module of the Advanced Resistive Exercise Device (ARED) Using Adams

NASA's Digital Astronaut Project (DAP) implements well-vetted computational models to predict and assess spaceflight health and performance risks, and enhance countermeasure development. DAP provides expertise and computation tools to its research customers for model development, integration, or analysis. DAP is currently supporting the NASA Exercise Physiology and Countermeasures (ExPC) project by integrating their biomechanical models of specific exercise movements with dynamic models of the devices on which the exercises were performed. This presentation focuses on the development of a high fidelity dynamic module of the Advanced Resistive Exercise Device (ARED) on board the ISS. The ARED module, illustrated in the figure below, was developed using the Adams (MSC Santa Ana, California) simulation package. The Adams package provides the capabilities to perform multi rigid body, flexible body, and mixed dynamic analyses of complex mechanisms. These capabilities were applied to accurately simulate: Inertial and mass properties of the device such as the vibration isolation system (VIS) effects and other ARED components, Non-linear joint friction effects, The gas law dynamics of the vacuum cylinders and VIS components using custom written differential state equations, The ARED flywheel dynamics, including torque limiting clutch. Design data from the JSC ARED Engineering team was utilized in developing the model. This included solid modeling geometry files, component/system specifications, engineering reports and available data sets. The Adams ARED module is importable into LifeMOD (Life Modeler, Inc., San Clemente, CA) for biomechanical analyses of different resistive exercises such as squat and dead-lift. Using motion capture data from ground test subjects, the ExPC developed biomechanical exercise models in LifeMOD. The Adams ARED device module was then integrated with the exercise subject model into one integrated dynamic model. This presentation will describe the development of the Adams ARED module including its capabilities, limitations, and assumptions. Preliminary results, validation activities, and a practical application of the module to inform the relative effect of the flywheels on exercise will be discussed.

Humphreys, B. T.↗
NASA NTRS1994

Non-subjective cataract analysis and its application in space radiation risk assessment

Experimental animal studies and human observations suggest that the question is not whether or not prolonged space missions will cause cataracts to appear prematurely in the astronauts, but when and to what degree. Historically the major impediment to radiation cataract follow-up has been the necessarily subjective nature of assessing the degree of lens transparency. This has spurred the development of instruments which produce video images amenable to digital analysis. One such system, the Zeiss Scheimpflug slit lamp measuring system (SLC), was incorporated into our ongoing studies of radiation cataractogenesis. It was found that the Zeiss SLC measuring system has high resolution and permits the acquisition of reproducible images of the anterior segment of the eye. Our results, based on about 650 images of the rats lens, and followed over a period of 91 weeks of radiation cataract development, showed that the Integrated Optical Density (IOD) of the lens correlated well with conventional assessment with the added advantages of objectivity, permanent and transportable records and linearity as cataracts become more severe. This continuous data acquisition, commencing with cataract onset, can proceed through more advanced stages. The SLC exhibits much greater sensitivity reflected in a continuously progressive severity despite the artifactual plateaus in staging which occur using conventional scoring methods. Systems such as the Zeiss SLC should be used to monitor astronauts frequent visits to low earth orbit to obtain a longitudinal data-base on the influence of this activity on the lens.

Wu, B.↗
NASA NTRS2006

Comprehensive Astronaut Immune Assessment Following a Short-Duration Space Flight

Immune system dysregulation has been demonstrated to occur during spaceflight and has the potential to cause serious health risks to crewmembers participating in exploration class missions. As a part of an ongoing NASA flight experiment assessing viral immunity (DSO-500), a generalized immune assessment was performed on 3 crewmembers who participated in the recent STS-114 Space Shuttle mission. The following assays were performed: (1) comprehensive immunophenotype analysis; (2) T cell function/intracellular cytokine profiles; (4) secreted Th1/Th2 cytokine profiles via cytometric bead array. Immunophenotype analysis included a leukocyte differential, lymphocyte subsets, T cell subsets, cytotoxic/effector CD8+ T cells, memory/naive T cell subsets and constitutively activated T cells. Study timepoints were L-180, L-65, L-10, R+0, R+3 and R+14. Detailed data are presented in the poster text. As expected from a limited number of human subjects, data tended to vary with respect to most parameters. Specific post-flight alterations were as follows (subject number in parentheses): Granulocytosis (2/3), reduced NK cells (3/3), elevated CD4/CD8 ratio (3/3), general CD8+ phenotype shift to a less differentiated phenotype (3/3), elevated levels of memory CD4+ T cells (3/3), loss of L-selectin on T cell subsets (3/3), increased levels of activated T cells (2/3), reduced IL-2 producing T cell subsets (3/3), levels of IFNg producing T cells were unchanged. CD8+ T cell expression of the CD69 activation markers following whole blood stimulation with SEA+SEB were dramatically reduced postflight (3/3), whereas other T cell function assessments were largely unchanged. Cytometric bead array assessment of secreted T cell cytokines was performed, following whole blood stimulation with either CD3/CD28 antibodies or PMA+ionomycin for 48 hours. Specific cytokines assessed were IFNg, TNFa, IL-2, IL-4, IL-5, IL-10. Following CD3/CD28 stimulation, all three crewmembers had a mission-associated reduction in the levels of secreted IFNg. One crewmember had a post-flight inversion in the IFNg/IL-10 ratio postflight, which trended back to baseline by R+14. Detailed cytokine data are presented in the poster text. This testing regimen was designed to correlate immunophenotype changes (thought to correspond to specific in-vivo immune responses or pathogenesis), against altered leukocyte function and cytokine profiles. In-flight studies are required to determine if post-flight alterations are reflective of the in-flight condition, or are a response to landing and readaptation.

Crucian, Brian↗
NASA NTRSDate not supplied

Prediction of Calcium Oxalate Stone Risk with Interventions

Introduction Mitigations intended to reduce bone mineral loss in-flight also influence the level of renal stone risk to astronauts. Extending a recent study completed by our group [1], we investigate the likely influence of combined fluid intake and Ca excretion mitigation strategies. Methods A computational biochemistry model representing CaOx crystal precipitation, growth, and agglomeration [2] is combined with a probabilistic analysis to predict the in-flight CaOx renal stone incidence risk ratio (IRR) relative to pre-flight values using 1517 astronaut 24-hour urine chemistries. The output of this simulation is used to assess the combined impact of controlling fluid intake and Ca excretion on maintaining IRR < 1.2 for > 95% of the population, a threshold determined from initial analysis of the model output compared to referent populations [1]. Results and Conclusions Figure 1 illustrates the simulated in-flight astronaut population (n=40000) with CaOx IRR > 1.2. The red lines indicate the known clinical risk boundary of each factor, and the white box is considered the area of high combined clinical risk. The simulation and identified risk threshold conform well to the expected clinical risk boundaries. The results, assuming insensible water losses equal or exceed 0.7 L/day, imply mitigations achieve risks similar to pre-flight levels when either Ca < 150 mg/day or fluid volume intake > 3.2 L/day individually, or combined Ca < 200 and fluid volume intake > 2.5 L/day. We continue to investigate similar compounded effects and look to apprise engineering trades by informing relative risk changes during mission design. References [1] D. A. Goodenow-Messman, S. A. Gokoglu, M. Kassemi, and J. Myers, Jerry G., “Characterization of Astronaut CaOx Renal Stone Incidence Rates to Quantify In-flight and Post-flight Relative Risk,” npj Microgravity, in review, 2021. [2] M. Kassemi and D. Thompson, “Prediction of renal crystalline size distributions in space using a PBE analytic model. 1. Effect of microgravity-induced biochemical alterations,” Am. J. Physiol. Physiol., vol. 311, no. 3, pp. F520–F530, Sep. 2016, doi: 10.1152/ajprenal.00401.2015.

Debra A Goodenow↗
NASA NTRS2009

Renal Stone Risk during Spaceflight: Assessment and Countermeasure Validation

NASA's Vision for Space Exploration centers on exploration class missions including the goals of returning to the moon and landing on Mars. One of NASA's objectives is to focus research on astronaut health and the development of countermeasures that will protect crewmembers during long duration voyages. Exposure to microgravity affects human physiology and results in changes in the urinary chemical composition favoring urinary supersaturation and an increased risk of stone formation. Nephrolithiasis is a multifactorial disease and development of a renal stone is significantly influenced by both dietary and environmental factors. Previous results from long duration Mir and short duration Shuttle missions have shown decreased urine volume, pH, and citrate levels and increased calcium. Citrate, an important inhibitor of calcium-containing stones, binds with urinary calcium reducing the amount of calcium available to form stones. Citrate inhibits renal stone recurrence by preventing crystal growth, aggregation, and nucleation and is one of the most common therapeutic agents used to prevent stone formation. Methods: Thirty long duration crewmembers (29 male, 1 female) participated in this study. 24-hour urines were collected and dietary monitoring was performed pre-, in-, and postflight. Crewmembers in the treatment group received two potassium citrate (KCIT) pills, 10 mEq/pill, ingested daily beginning 3 days before launch, all in-flight days and through 14 days postflight. Urinary biochemical and dietary analyses were completed. Results: KCIT treated subjects exhibited decreased urinary calcium excretion and maintained the levels of calcium oxalate supersaturation risk at their preflight levels. The increased urinary pH levels in these subjects reduced the risk of uric acid stones. Discussion: The current study investigated the use of potassium citrate as a countermeasure to minimize the risk of stone formation during ISS missions. Results suggest that supplementation with potassium citrate decreases the risk of stone formation during and immediately after spaceflight.

Whitson, Peggy A.↗