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At least 343 records · Page 19

Fatigue in U.S. Astronauts Onboard the International Space Station: Environmental factors, Operational Impacts, and Implementation of Countermeasures

Crewmembers have experienced fatigue for reasons similar to military deployments. Astronauts experience psychological stressors such as: heavy workloads, extended duty periods, circadian misalignment, inadequate/ineffective sleep, distracting background noise, unexpected and variable mission schedules, unfavorable thermal control, unusual sleep environment with schedules that impinge on pre‐sleep periods.

Scheuring, R. A.↗

Human Health Countermeasures - Partial-Gravity Analogs Workshop

The experimental conditions that were deemed the most interesting by the HHC Element lead scientists are those permitting studies of the long-term effects of exposure to (a) chronic rotation when supine or in head down tilt (ground-based); and (b) long-radius centrifugation (space based). It is interesting to note that chronic ground based slow rotation room studies have not been performed since the 1960's, when the USA and USSR were investigating the potential use of AG for long-duration space missions. On the other hand, the other partial gravity analogs, i.e., parabolic flight, HUT, suspension, and short-radius centrifugation, have been regularly used in the last three decades (see review in Clément et al. 2015). Based on the workshop evaluations and the scores by the HHC scientific disciplines indicated in tables 3 and 4, simulation of partial G between 0 and 1 should be prioritized as follows: Priority 1. Chronic space-based partial-G analogs: a. Chronic space-based long-radius centrifugation. The ideal scenario would be chronic long-radius centrifugation of cells, animals and humans in a translational research approach - ideally beyond low earth orbit under deep space environmental effects and at various rotations - to obtain different G-effects. In this scenario, all physiological systems could be evaluated and the relationship between physiological response and G level established. This would be the most integrative way of defining, for the first time ever, G-thresholds for each physiological system. b. Chronic space-based centrifugation of animals. Chronic centrifugation of rodents at various G levels in space would allow for determination of AG thresholds of protection for each physiological system. In this case, all physiological systems will be of interest. Intermittent centrifugation will be of secondary interest. c. Chronic space-based centrifugation of cell cultures (RWV). Bioreactor studies of cells and cell cultures of various tissues at various G levels would allow for intracellular investigations of the effects of partial-G. Priority 2. Acute, intermittent space based partial-G analogs: a. Acute, intermittent space-based short radius human centrifugation. Intermittent centrifugation of humans would allow determination of thresholds of AG for protection of astronaut health in space. Priority 3. Chronic ground-based partial-G analogs: a. Chronic centrifugation of supine or head-down tilted humans. b. Chronic head-up tilt in humans. c. Chronic head-out graded dry immersion in humans. d. Chronic partial suspension of rodents e. Chronic rotating bioreactor cell culture studies (RWV) Priority 4. Acute ground based partial-G analogs. a. Parabolic flights. Very acute and short term effects of G levels between 0 and 1 in humans for fast responding systems like cardiovascular and sensorimotor as well as for acute responses in cell cultures and animals. b. Other acute models as indicated in table 3.

Barr, Yael↗

Effect of Dietary Countermeasures and Impact of Gravity on Renal Calculi Size Distributions Predicted by PBE-System and PBE-CFD Models

Renal stone disease is not only a concern on earth but can conceivably pose a serious risk to the astronauts health and safety in Space. In this work, two different deterministic models based on a Population Balance Equation (PBE) analysis of renal stone formation are developed to assess the risks of critical renal stone incidence for astronauts during space travel. In the first model, the nephron is treated as a continuous mixed suspension mixed product removal crystallizer and the PBE for the nucleating, growing and agglomerating renal calculi is coupled to speciation calculations performed by JESS. Predictions of stone size distributions in the kidney using this model indicate that the astronaut in microgravity is at noticeably greater but still subcritical risk and recommend administration of citrate and augmented hydration as effective means of minimizing and containing this risk. In the second model, the PBE analysis is coupled to a Computational Fluid Dynamics (CFD) model for flow of urine and transport of Calcium and Oxalate in the nephron to predict the impact of gravity on the stone size distributions. Results presented for realistic 3D tubule and collecting duct geometries, clearly indicate that agglomeration is the primary mode of size enhancement in both 1g and microgravity. 3D numerical simulations seem to further indicate that there will be an increased number of smaller stones developed in microgravity that will likely pass through the nephron in the absence of wall adhesion. However, upon reentry to a 1g (Earth) or 38g (Mars) partial gravitational fields, the renal calculi can lag behind the urinary flow in tubules that are adversely oriented with respect to the gravitational field and grow agglomerate to large sizes that are sedimented near the wall with increased propensity for wall adhesion, plaque formation, and risk to the astronauts.

Renal Stones↗

Stroboscopic Goggles as a Countermeasure for Dynamic Visual Acuity and Landing Sickness After Long-Duration Spaceflight

Gravity transitions cause changes in the vestibulo-occular reflex (VOR), which manifests as poor gaze control, a decrement in dynamic visual acuity (the ability to maintain gaze while in motion), both of which are caused by retinal slip. Retinal slip, the inability to keep an image focused on the retina, can drive or worsen sensory conflict, resulting in motion sickness (MS). Currently 100% of returning crewmembers report MS symptoms, which might affect their ability to perform mission critical tasks immediately after landing. Reschke et al. (2007) demonstrate that stroboscopic vision goggles improve motion sickness onset and symptom severity in motion sickness driven by retinal slip.

Rosenberg, M. J. F.↗

Non-Pharmacological Countermeasure to Decrease Landing Sickness and Improve Functional Performance

Upon return from long-duration spaceflight, 100% of crewmembers experience motion sickness (MS) symptoms. The interactions between crewmembers' adaptation to a gravitational transition, the performance decrements resulting from MS and/or use of promethazine (PMZ), and the constraints imposed by mission task demands could significantly challenge and limit an astronaut's ability to perform functional tasks during gravitational transitions. Stochastic resonance (SR) is "noise benefit": adding noise to a system might increase the information (examples to the left and above). Stochastic vestibular stimulation (SVS), or low levels of noise applied to the vestibular system, improves balance and locomotor performance (Goel et al. 2015, Mulavara et al. 2011, 2015). In hemi-lesioned rat models, Samoudi et al. 2012 found that SVS increased GABA release on the lesioned, but not the intact side. Activation of the GABA pathway is important in modulating MS and promoting adaptability (Cohen 2008) and was seen to reverse MS symptoms in rats after unilateral labyrinthectomy (Magnusson et al. 2000). Thus, SVS could be used to promote GABA pathways to reduce MS and promote adaptability, eliminate the need for PMZ or other performance-inhibiting drugs.

Rosenberg, M. J. F.↗