EXPERIMENTAL ANIMAL DECOMPRESSIONS TO A NEAR VACUUM ENVIRONMENT.
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In 1985, Rockwell International (now Boeing--North American) completed the Space Station Crew Safety Alternatives Study for NASA. This five-volume study identified a wide range of potential safety threats and hazards that the crew might encounter on the future International Space Station. These threats included fire, explosion, collision, decompression, contamination, and radiation, among many others. One volume focused on the human factors aspects of safety, featuring the Crew Safety-Human Factors Interaction Model. In this model, a stressor (such as one of the threats) can lead to degraded performance, which can contribute to human error, unless appropriate and effective countermeasures are available to the crew. In 1986, the Soviet Union launched the Mir Space Station, the "second generation" that followed the Salyut series of space stations. The Mir was designed for a five-year life on orbit. It remained in use for fourteen years. During the first ten years, it performed well, with few safety issues. However, during the last four years, the aging station--operating at more than two times beyond its design lifetime--encountered a variety of safety hazards and human factors issues. Despite these often serious problems, the Mir crews always found a way to save the station, and no crew member was seriously injured or killed. This paper evaluates the safety record on Mir, and compares it to the NASA-Rockwell study, that was contemporaneous with the construction and launch of Mir. This comparison and analysis can provide a foundation for future space crew safety and related human factors support.
A concern in the past regarding contact lens wear in aviation has been the fear of subcontact lens bubble formation. Previous reports have documented the occurrence of bubbles with hard (PMMA) lenses. Reported here are the results of contact lens bubble studies with soft hydrophilic and rigid gas-permeable lenses. Testing was accomplished in hypobaric chambers and onboard USAF transport aircraft. Hypobaric chamber flights were of three types: high-altitude flights up to 7,620 m (25,000 ft); explosive rapid decompressions from 2,438.4 m (8,000 ft) to 7,620 m (25,000 ft); and 4-h flights at 3,048 m (10,000 ft). Flights aboard transport aircraft typically had cabin pressures equivalent to 1,524-2,438.4 m (5,000-8,000 ft), and ranged in duration from 3 to 10 h. For subjects wearing rigid gas-permeable lenses, central bubbles were detected in 2 of 10 eyes and occurred at altitudes greater than 6,096 m (20,000 ft). With soft contact lenses, bubble formation was detected in approximately 24% (22 of 92 eyes) of the eyes tested, sometimes occurring at altitudes as low as 1,828.8 m (6,000 ft). Soft lens bubbles were always located at the limbus and were without sequela to vision or corneal epithelial integrity. Bubbles under the rigid lenses were primarily central, with potential adverse effects on vision and the corneal epithelium.
Following a rapid decompression in an altitude chamber for routine training purposes, a 38-year-old altitude chamber technician developed rapid onset of mental dullness, right arm weakness, and sensory deficits. Immediate treatment with compression therapy in a hyperbaric chamber resulted in complete resolution. Ambient pressure changes great enough to result in arterial air embolism due to an explosive or rapid decompression have been described as a potential hazard in aviation, although no actual cases of such a phenomenon have been previously reported. The aeromedical considerations of this complication are discussed.
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Explosive volcanic eruptions are driven by exsolution of H2O-rich vapour from silicic magma. Eruption dynamics involve a complex interplay between nucleation and growth of vapour bubbles and crystallization, generating highly nonlinear variation in the physical properties of magma as it ascends beneath a volcano. This makes explosive volcanism difficult to model and, ultimately, to predict. A key unknown is the temperature variation in magma rising through the sub-volcanic system, as it loses gas and crystallizes en route. Thermodynamic modelling of magma that degasses, but does not crystallize, indicates that both cooling and heating are possible. Hitherto it has not been possible to evaluate such alternatives because of the difficulty of tracking temperature variations in moving magma several kilometres below the surface. Here we extend recent work on glassy melt inclusions trapped in plagioclase crystals to develop a method for tracking pressure-temperature-crystallinity paths in magma beneath two active andesite volcanoes. We use dissolved H2O in melt inclusions to constrain the pressure of H2O at the time an inclusion became sealed, incompatible trace element concentrations to calculate the corresponding magma crystallinity and plagioclase-melt geothermometry to determine the temperature. These data are allied to ilmenite-magnetite geothermometry to show that the temperature of ascending magma increases by up to 100 degrees C, owing to the release of latent heat of crystallization. This heating can account for several common textural features of andesitic magmas, which might otherwise be erroneously attributed to pre-eruptive magma mixing.
Biodynamics measures the effects of mechanical force on living tissues. The quantitative relations of mechanical stress factors and biological strain responses of the living body provide criteria for limits of injury threshold, reversible injury, permanently disabling injury, and fatal injury. These criteria are guidelines for aerospace design and performance standards involving human survival in the environment of flight. Below these limits, the effects of mechanical force factors on human performance while acutely or chronically exposed to them in aerial or space flight are crucial. Some can be accumulatively disabling; others can be adapted to over a period of time. Extremes of low-frequency vibration cannot be long endured, while sustained zero gravity in space flight produces mild, transient malaise followed by adaptation in several hours. Aerospace flight biodynamics deals with human reactions to absence of gravity; sustained curvilinear acceleration; sustained acceleration and deceleration (launch and reentry in space flight); single impact force (collisions); low-frequency vibration in the whole human body resonance response range; whole-body tumbling and spinning, as in high-altitude free-fall; acoustical range vibrations; explosive blast in air or water; abrupt decompression, as in cabin pressure failure; static forces in tension, compression, torsion and shear. Biodynamic stress analysis takes into account whole-body responses, particular responses of rigid bone, viscous elastic soft tissues, pneumatic and hydraulic effects of gas and fluids in hollow organs, and displacements of solid organs suspended in body cavities. Accurate and comprehensive results require physical measurements, clinical and laboratory studies before and after exposure, subjective reports of trained volunteer subjects, and objective medical and bioengineering evaluation of results.(ABSTRACT TRUNCATED AT 250 WORDS)
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In Hannover/Germany in 1976 a so called "Society for Regenerative Hyperbaric Therapy" (Gesellschaft für Regenerative Uberdruck-Therapie) subjected 20 patients within two coupled multi-place chambers to a simulated hyperbaric environment, equivalent to a maximum of 4 ata, followed usually by gradual reductions of the pressure. The patients were of an average age of 67.2 years and were afflicted by various disorders. During one of the "dives" a patient developed air embolism of the central nervous system. During ensuing confusion of the chamber was opened suddenly, with resultant explosive reduction of the high pressure. This resulted in five letal accidents of decompression sickness. Post mortem examination revealed diffuse distribution of gas bubbles throughout the entire body. By elecronmicroscopy each bubble was covered by an osmiophilic coat. Post mortem findings are discussed and correlated with well-known and new clinical symptomes. These observations present for the first time fatal accidents of decompression sickness in humans, associated with hyperbaric air-therapy.
Recreational scuba diving has continued to grow in popularity in the past several decades, and military diving remains an integral part of ship husbandry, explosives and ordinance disposal, and special warfare. Although relatively uncommon, disorders such as decompression sickness and arterial gas embolism can be fatal, whereas disorders such as ear baro-trauma and dysbaric osteonecrosis are not fatal but can cause significant morbidity. An extensive literature search was performed to comprehensively examine the current role of diagnostic radiology with respect to diving medicine. In selected cases, diagnostic imaging can be of potential benefit for evaluation. Diagnostic imaging plays a useful role in the screening of certain individuals for future fitness to dive. Radiological imaging has also been of paramount importance in postmortem evaluation of dive casualties.
Explosion injury to the intestinal tract resulting from electrocautery is a rare occurrence. Only two small bowel explosions have been described previously. Here we describe an explosion of small bowel during strictureplasty in a patient with chronic obstructing Crohn's disease. Recommendations to avoid this disastrous complication include proximal decompression prior to incision and, in some cases, it may be wise to avoid electrocautery altogether.
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Recent undersea experiments in the United States and France showed that divers can live and work effectively for many days from dwellings placed on the continental shelf to depths down to 432 feet. If prolonged exposure to the hostile underwater environment is to be tolerated successfully, existing physical, biological and equipment hazards must be recognized, prepared for and, when possible, circumvented.
The factors relating to the clinical outcome of an industrial aerosol plant explosion are reviewed. Eighteen of 24 workers inside the plant required hospitalization and five died. Proximity to the blast was associated with extensive injuries unless workers were shielded by physical barriers or partitions. Burn severity and mortality were increased in those wearing synthetic garments compared to their counterparts wearing fiber clothing. Facial burns occurred in all unprotected workers. Forearm and hand burns in 11 patients required decompressive escharotomies. Topical treatment with silver sulfadiazine was associated with more significant leukopenia and neutropenia than treatment with silver nitrate. We conclude that industrial design should include safeguards which isolate workers from flammable materials, including isolation of explosive materials from working areas, alarm systems to detect leakage of flammable agents, protective barriers and shields, and the regulation and institution of flame and flash-resistant clothing.
During a thirty month period, 319 patients underwent open heart operations, and of these, three experienced a life-threatening explosive abdominal catastrophe. Aggressive radiographic maneuvers established the diagnosis of gastroduodenal perforation. Appropriate abdominal surgery with plication of the perforation and, whenever possible, the establishment of tube gastrostomy for decompression and a tube jejunostomy for feeding is desirable. All three patients required mechanical ventilatory support and tracheostomy prior to the abdominal catastrophe. Prophylactic antacids and sedation seem appropriate, particularly for selected patients (those with a prior peptic history and those with pulmonary dysfunction). Pulmonary toilet for those identified by preoperative pulmonary screening may circumvent the need for postoperative ventilatory support, which increases the risk of stress ulceration. Of the three patients described, all survived the gastrointestinal surgery but only one left the hospital. One died twenty days and another forty-eight days after the intestinal surgery, both of pneumonitis and septicemia.