Mitigating Decompression Sickness for Moon and Mars
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Alejandro Garbino↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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An Evaluation of Algorithms and Methods for Compressing and Decompressing Atmospheric Transmission Data for Use in At-Sensor Measurements.
Abstract not provided.
Van Benthem, Mark Hilary↗
An Evaluation of Algorithms and Methods for Compressing and Decompressing Atmospheric Transmission Data for Use in At-Sensor Measurements.
Abstract not provided.
Van Benthem, Mark Hilary↗
Parallelization of Variable Rate Decompression through Side Channel Information
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Computer science↗
Phase transformations, microstructural refinement and defect evolution mechanisms in Al-Si alloys under non-hydrostatic diamond anvil cell compression
Non-hydrostatic compression of materials using a diamond anvil cell (DAC) can transform equilibrium microstructure of an alloy to novel, potentially metastable states. In this study, in situ synchrotron X-ray diffraction (XRD) during compression up to 24 GPa and subsequent ex situ, high resolution analytical electron microscopy (AEM) after decompression of an Al-Si alloy provided insight into the crystallographic changes during the compression as well as microstructural refinement, and defect structures caused by such a high pressure compression-decompression process. Pressure resolved in-situ synchrotron XRD was used to detail the phase transformation pathway of the eutectic Si phase in Al-Si alloy, from Si-I → Si-XI → Si-V during compression, and a final transformation predominantly to Si-III after decompression. Using scanning and transmission electron microscopy (S/TEM), site specific analysis of the alloy immediately underneath the anvil contact surface demonstrated a highly complex microstructure. A narrow region of thick amorphous Al oxide interspersed with nanocrystalline grains was found at the top surface. Underneath this Al oxide, while the majority the eutectic Si was transformed into highly-deformed, polycrystalline (PC) Si-III, a complex intermediate layer was discovered at the interface between Al and Si, comprised of a small fraction of Al nanocrystals and a majority of nanocrystalline Si-I. This combination of pressure resolved in-situ synchrotron XRD coupled with subsequent high resolution, electron microscopy resolved the phase transformation as well as non-equilibrium microstructures in a metallic alloy induced by a non-hydrostatic high pressure compression followed by decompression.
36 MATERIALS SCIENCE↗
STZ: A High Quality and High Speed Streaming Lossy Compression Framework for Scientific Data
Error-bounded lossy compression is one of the most efficient solutions to reduce the volume of scientific data. For lossy compression, progressive decompression and random-access decompression are critical features that enable on-demand data access and flexible analysis workflows. However, these features can severely degrade compression quality and speed. To address these limitations, we propose a novel streaming compression framework that supports both progressive decompression and random-access decompression while maintaining high compression quality and speed. Our contributions are three-fold: (1) we design the first compression framework that simultaneously enables both progressive decompression and random-access decompression; (2) we introduce a hierarchical partitioning strategy to enable both streaming features, along with a hierarchical prediction mechanism that mitigates the impact of partitioning and achieves high compression quality—even comparable to state-of-the-art (SOTA) non-streaming compressor SZ3; and (3) our framework delivers high compression and decompression speed, up to 6.7 × faster than SZ3.
Wang, Daoce [University of Nebraska, Omaha]↗
Using an Ultrasonic Instrument to Size Extravascular Bubbles
In an ongoing development project, microscopic bubbles in extravascular tissue in a human body will be detected by use of an enhanced version of the apparatus described in Ultrasonic Bubble- Sizing Instrument (MSC-22980), NASA Tech Briefs, Vol. 24, No. 10 (October 2000), page 62. To recapitulate: The physical basis of the instrument is the use of ultrasound to excite and measure the resonant behavior (oscillatory expansion and contraction) of bubbles. The resonant behavior is a function of the bubble diameter; the instrument exploits the diameter dependence of the resonance frequency and the general nonlinearity of the ultrasonic response of bubbles to detect bubbles and potentially measure their diameters. In the cited prior article, the application given most prominent mention was the measurement of gaseous emboli (essentially, gas bubbles in blood vessels) that cause decompression sickness and complications associated with cardiopulmonary surgery. According to the present proposal, the instrument capabilities would be extended to measure extravascular bubbles with diameters in the approximate range of 1 to 30 m. The proposed use of the instrument could contribute further to the understanding and prevention of decompression sickness: There is evidence that suggests that prebreathing oxygen greatly reduces the risk of decompression sickness by reducing the number of microscopic extravascular bubbles. By using the ultrasonic bubble-sizing instrument to detect and/or measure the sizes of such bubbles, it might be possible to predict the risk of decompression sickness. The instrument also has potential as a tool to guide the oxygen-prebreathing schedules of astronauts; high-altitude aviators; individuals who undertake high-altitude, low-opening (HALO) parachute jumps; and others at risk of decompression sickness. For example, an individual at serious risk of decompression sickness because of high concentrations of extravascular microscopic bubbles could be given a warning to continue to prebreathe oxygen until it was safe to decompress.
Magari, Patrick J.↗
A comparison of segmented abdominopelvic fluid volumes with conventional CT signs of abdominal compartment syndrome in a trauma population
Purpose: To compare the utility of abdominopelvic fluid volume measurements with established computed tomography signs for refractory post-traumatic abdominal compartment syndrome. Methods: This retrospective observational cohort study included 64 consecutive adult trauma patients with preoperative CT and diagnosis of refractory abdominal compartment syndrome requiring decompressive laparotomy at a level I trauma referral center between 2004 and 2014. We hypothesized that abdominal fluid volume measurements would be more predictive of the need for early laparotomy than previously described conventional CT signs of refractory ACS. Abdominopelvic fluid volumes were determined quantitatively using semi-automated segmentation software. The following conventional imaging parameters were recorded: abdominal anteroposterior:transverse ratio (round belly sign); infrahepatic vena cava diameter; distal abdominal aortic diameter; largest single small bowel wall diameter; hydronephrosis, inguinal herniation; and mesenteric and body wall edema. For outcome analysis, patients were stratified into two groups: those who underwent early (< 24 h) and late (≥ 24 h) decompressive laparotomy following CT. Correlation analysis, comparison of means, and multivariate logistic regression were performed. Results: Abdominal fluid volumes (p = 0.001) and anteroposterior:transverse ratio (p = 0.009) were increased and inferior vena cava diameter (p = 0.009) was decreased in the early decompressive laparotomy group. Multivariate analysis including conventional CT variables, fluid volumes, and laboratory values revealed abdominal fluid volumes (p = 0.012; Δ in log odds of 1.002/mL) as the only independent predictor of early decompressive laparotomy. Conclusions: Segmented abdominopelvic free fluid volumes had greater predictive utility for decision to perform early decompressive laparotomy than previously described ACS-related CT signs in trauma patients who developed refractory abdominal compartment syndrome.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
The high pressure phase transformation behavior of silicon nanowires
Si nanowires of 80–150 nm and 200–250 nm diameter are pressurized up to 22 GPa using a diamond anvil cell. Raman and x-ray diffraction data were collected during both compression and decompression. Electron microscopy images reveal that the nanowires retain a nanowire-like morphology (after high pressure treatment). On compression, dc-Si was observed to persist at pressures up to 19 GPa compared to ~11 GPa for bulk-Si. On decompression, the metallic β-Sn phase was found to be more stable for Si nanowires compared with bulk-Si when lowering the pressure and was observed as low as 6 GPa. For the smallest nanowires studied (80–150 nm), predominately a-Si was obtained on decompression, whereas for larger nanowires (200–250 nm), clear evidence for the r8/bc8-Si phase was obtained. We suggest that the small volume of the individual Si nanowires compared with bulk-Si inhibits the nucleation of the r8-Si phase on decompression. This study shows that there is a size dependence in the high pressure behavior of Si nanowires during both compression and decompression.
36 MATERIALS SCIENCE↗
Predicting hydraulic structure-induced barotrauma in Australian fish species
When fish pass downstream through river infrastructure, such as dams and weirs, barotrauma may occur due to rapid decompression. In severe cases, barotrauma may lead to mortality. Different species likely respond differently to these decompressions. Therefore, to predict barotrauma for a specific species, surrogate species may not be a valid approach, and it may be necessary to examine each species individually. For this study, Australian bass and carp gudgeon were exposed to a range of rapid decompressions using hyper/hypobaric hydro-chambers and examined for injuries and mortality. Rapid decompression data from these two fish species, in addition to previously examined Murray cod and silver perch were evaluated to determine which injuries were highly associated with and likely to predict mortality. Dose-response logistic regressions models were developed for each species to predict injury and mortality over a range of rapid decompressions. These models are valuable for estimating injury and mortality rates for fish passing though river infrastructure and can be applied to specific sites where pressure profiles have been developed. Applying these models to current and future infrastructure can provide important insight into what measures or design alterations may be necessary to reduce negative impacts of infrastructure on fish populations.
Pflugrath, Brett D.↗
Doppler indices of gas phase formation in hypobaric environments: Time-intensity analysis
A semi-quantitative method to analyze decompression data is described. It possesses the advantage that it allows a graded response to decompression rather than the dichotomous response generally employed. A generalized critical volume (C-V), or stoichiometric time-dependent equilibrium model is examined that relates the constant of the equation P sub i equals m P sub f plus b to variable tissue supersaturation and gas washout terms. The effects of the tissue ratio on gas phase formation indicate that a decreased ratio yields fewer individuals with Doppler detectable gas bubbles, but those individuals still present with Spencer Grade 3 or 4. This might indicate a local collapse of tissue saturation. The individuals with Grade 3 or 4 could be at risk for type 2 decompression sickness by transpulmonic arterialization. The primary regulator of the problems of decompression sickness is the reduction of local supersaturation, presumably governed by the presence and number of gas micronuclei. It is postulated that a reduction in these nuclei will favor a low incidence of decompression sickness in microgravity secondary to hypokinesia and adynamia.
Powell, Michael R.↗
Cardiovascular Deconditioning and Venous Air Embolism in Simulated Microgravity in the Rat
Astronauts conducting extravehicular activities undergo decompression to a lower ambient pressure, potentially resulting in gas bubble formation within the tissues and venous circulation. Additionally, exposure to microgravity produces fluid shifts within the body leading to cardiovascular deconditioning. A lower incidence of decompression illness in actual spaceflight compared with that in ground-based altitude chamber flights suggests that there is a possible interaction between microgravity exposure and decompression illness. The purpose of this study was to evaluate the cardiovascular and pulmonary effects of simulated hypobaric decompression stress using a tail suspension (head-down tilt) model of microgravity to produce the fluid shifts associated with weightlessness in conscious, chronically instrumented rats. Venous bubble formation resulting from altitude decompression illness was simulated by a 3-h intravenous air infusion. Cardiovascular deconditioning was simulated by 96 h of head-down tilt. Heart rate, mean arterial blood pressure, central venous pressure, left ventricular wall thickening and cardiac output were continuously recorded. Lung studies were performed to evaluate edema formation and compliance measurement. Blood and pleural fluid were examined for changes in white cell counts and protein concentration. Our data demonstrated that in tail-suspended rats subjected to venous air infusions, there was a reduction in pulmonary edema formation and less of a decrease in cardiac output than occurred following venous air infusion alone. Mean arterial blood pressure and myocardial wall thickening fractions were unchanged with either tail-suspension or venous air infusion. Heart rate decreased in both conditions while systemic vascular resistance increased. These differences may be due in part to a change or redistribution of pulmonary blood flow or to a diminished cellular response to the microvascular insult of the venous air embolization.
Robinson, R. R.↗
Breathing 100% oxygen compared with 50% oxygen: 50% nitrogen reduces altitude-induced venous gas emboli
The risk of venous gas emboli (VGE) and decompression sickness (DCS) must be determined before selection of the lowest pressure for an extravehicular activity (EVA) pressure suit which eliminates the requirement for prebreathing. In earlier studies, use of a 50% oxygen:50% nitrogen breathing mixture (50:50 mix) during 139 zero-prebreathe decompressions of male subjects to 8.3-7.8 psia resulted in 51 instances of severe VGE and one case of DCS. Our current study investigated effects of 40 zero-prebreathe decompressions of male subjects to 8.3-6.8 psia for 6 h while breathing 100% oxygen and performing moderate exercise. No DCS symptoms were observed. Severe VGE were not detected at 8.3 psia, but were present during 10%, 20%, and 40% of the exposures at 7.8, 7.3, and 6.8 psia, respectively. Zero-prebreathe decompression while breathing 100% oxygen results in significantly lower VGE and DCS risk levels than while breathing a 50:50 mix. Our results show that 7.3 psia EVA pressure suits with 100% oxygen should be safer than 8.3 psia suits with a 50:50 mix.
NASA Program Environmental Health↗
Determining Barotrauma in the Pictus Catfish, Pimelodus pictus, Experimentally Exposed to Simulated Hydropower Turbine Passage
Hydropower capacity is to be developed by 73% globally. This great development poses severe threats to the aquatic diversity and ecosystems services. Downstream passage of fish through turbines and the entrance at the draft tube are important impacts affecting the fish diversity. During such events, fish suffer rapid decompression, which can lead to barotrauma and mortality. Despite the magnitude of mortality events, data to understand barotrauma on fish is scarce and largely focused in salmonids. This study aimed to evaluate the effects of rapid decompression on the Amazonian benthic species Pimelodus pictus, simulated in hypo-hyperbaric chambers. All fish were negatively buoyant throughout the experiments, hindering the calculation of the ratio of pressure change and posing challenges to data analysis. Instead, the pressure of neutral buoyancy and time to decompression were used to establish the likelihood of barotrauma. The most frequent injuries in P. pictus were swim bladder rupture, intestine rupture, internal hemorrhage and embolism. The occurrence and magnitude of those injuries were related to the pressure of neutral buoyancy, pressure variation and time to decompression. Barotrauma studies with benthic fish species deemed to be challenging and are likely to require the use of complementary approaches on such species.
Do Vale Beirao, Bernardo↗
STRONG SOLAR WIND DYNAMIC PRESSURE PULSES: INTERPLANETARY SOURCES AND THEIR IMPACTS ON GEOSYNCHRONOUS MAGNETIC FIELDS
In this investigation, we first present a statistical result of the interplanetary sources of very strong solar wind dynamic pressure pulses (DPPs) detected by WIND during solar cycle 23. It is found that the vast majority of strong DPPs reside within solar wind disturbances. Although the variabilities of geosynchronous magnetic fields (GMFs) due to the impact of positive DPPs have been well established, there appears to be no systematic investigations on the response of GMFs to negative DPPs. Here, we study both the decompression effects of very strong negative DPPs and the compression from strong positive DPPs on GMFs at different magnetic local time sectors. In response to the decompression of strong negative DPPs, GMFs on the dayside near dawn and near dusk on the nightside, are generally depressed. But near the midnight region, the responses of GMF are very diverse, being either positive or negative. For part of the events when GOES is located at the midnight sector, the GMF is found to abnormally increase as the result of magnetospheric decompression caused by negative DPPs. It is known that under certain conditions magnetic depression of nightside GMFs can be caused by the impact of positive DPPs. Here, we find that a stronger pressure enhancement may have a higher probability of producing the exceptional depression of GMF at the midnight region. Statistically, both the decompression effect of strong negative DPPs and the compression effect of strong positive DPPs depend on the magnetic local time, which are stronger at the noon sector.
79 ASTRONOMY AND ASTROPHYSICS↗
WE-A-17A-11: Implanted Brachytherapy Seed Movement Due to Transrectal Ultrasound Probe-Induced Prostate Deformation
Purpose: To characterize the movement of implanted brachytherapy seeds due to transrectal ultrasound probe-induced prostate deformation and to estimate the effects on prostate dosimetry. Methods: Implanted probe-in and probe-removed seed distributions were reconstructed for 10 patients using C-arm fluoroscopy imaging. The prostate was delineated on ultrasound and registered to the fluoroscopy seeds using a visible subset of seeds and residual needle tracks. A linear tensor and shearing model correlated the seed movement with position. The seed movement model was used to infer the underlying prostate deformation and to simulate the prostate contour without probe compression. Changes in prostate and surrogate urethra dosimetry were calculated. Results: Seed movement patterns reflecting elastic decompression, lateral shearing, and rectal bending were observed. Elastic decompression was characterized by anterior-posterior expansion and superior-inferior and lateral contractions. For lateral shearing, anterior movement up to 6 mm was observed for extraprostatic seeds in the lateral peripheral region. The average intra-prostatic seed movement was 1.3 mm, and the residual after linear modeling was 0.6 mm. Prostate D90 increased by 4 Gy on average (8 Gy max) and was correlated with elastic decompression. For selected patients, lateral shearing resulted in differential change in D90 of 7 Gy between anterior and posterior quadrants, and increase in whole prostate D90 of 4 Gy. Urethra D10 increased by 4 Gy. Conclusion: Seed movement upon probe removal was characterized. The proposed model captured the linear correlation between seed movement and position. Whole prostate dose coverage increased slightly, due to the small but systematic seed movement associated with elastic decompression. Lateral shearing movement increased dose coverage in the anterior-lateral region, at the expense of the posterior-lateral region. The effect on whole prostate D90 was smaller due to the subset of peripheral seeds involved, but lateral shearing movement can have greater consequences for local dose coverage.
60 APPLIED LIFE SCIENCES↗