Performing a surgical procedure during spaceflight will become more likely in the future as the duration of missions becomes longer. Only minimal surgical capability was available on previous missions since the definitive medical care time was short and the likelihood of a surgical event too low to justify carrying surgical hardware onboard. Early demonstrations of surgical procedures in the microgravity environment of parabolic flight indicated the need for careful logistical planning and restraint of surgical hardware. Human ergonomics also has more effect in microgravity than in the conventional 1-G environment. Three methods of surgical instrument restraint—a Minor Surgical Kit (MSK), a Surgical Restraint Scrub Suit (SRSS), and a Surgical Tray (ST)—were evaluated in parabolic flight surgical procedures. The MSK was easily stored, easily deployed, and demonstrated the best ability to facilitate a surgical procedure in microgravity. Important factors in a surgical restraint system for microgravity include excellent organization of supplies, ability to maintain sterility, accessibility while providing secure restraint, ability to dispose of sharp items and biological trash, and ergonomic efficiency.Abstract
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It has been shown that pointing movements are slowed during microgravity, however there is a paucity of corresponding data for other movement types. In our study, subjects pointed at visual targets without seeing their hand, and tracked targets moving around a circular path with and without hand vision, with and without a secondary reaction-time task. Pointing responses were slowed distinctly in microgravity, but the speed of tracking movements was not affected. The secondary task had comparable effects on tracking performance in space and on Earth. Response slowing in space is not due to an increased dependence on visual feedback, since it persists without hand vision. Differential effects of microgravity on pointing and tracking could be due to subjects' strategic decisions.Abstract
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Increased frequency and severity of herpesvirus infections are common in individuals with impaired cellular immunity, a phenomenon observed in both the elderly and astronauts alike. This study investigated immune responses and latent herpesvirus reactivation during a 9-d spaceflight. In addition, adrenocortical and immune responses of an elderly astronaut (payload specialist-2, PS2; age 77) who flew on this mission were compared with that of younger crewmembers. Spaceflight and associated stresses will decrease cellular immunity and reactivate latent herpesviruses. Blood and urine samples, collected from the seven crewmembers who flew on the Space Shuttle Discovery (STS-95), were analyzed for levels of neuroendocrine hormones, leukocyte and lymphocyte subsets, and evidence of herpesvirus reactivation. Prior to flight, increased antibody titers to latent Epstein-Barr virus were found. During flight, acute changes in dehydroepiandrosterone sulfate (DHEAS) and cortisol resulted in a pronounced decrease in the DHEAS/cortisol ratio by the end of the mission for PS2 and a younger crewmember. Shedding of cytomegalovirus (CMV) in urine and increased CMV antibody titers also occurred inflight. At landing, the percent increases in adrenocorticotropic hormone and cortisol were greatest for PS2 as compared with the other six crewmembers. A significant neutrophiIia also was observed in all crewmembers. Notably, PS2 had large increases in monocytes and natural killer cells at landing while other crewmembers showed little change or a decrease. These findings indicate that spaceflight and associated stresses reactivate latent herpesviruses and suggest that acute changes in neuroendocrine hormones mediate these changes in part by downregulating cellular immunity. Moreover, the similarities between aging and spaceflight suggest that the study of the immune system in elderly subjects may be useful as a predictive model for astronauts enduring long-term spaceflights.Abstract
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Research has demonstrated that exogenous adrenergic agonists produce dose-related vasoconstriction in men but not women. This suggests that the distribution of adrenergic receptor sites differ with gender. Women may have a higher density of receptor sites in the arterioles (fast acting with low gain) while men may have higher density in the larger vessels (slow acting with high gain). To partially test this hypothesis, the time course in beat-to-beat responses in systolic and diastolic BP, and heart rate was compared between six men and six women during the transition from a supine to an upright posture and during prolonged standing. The transient change in systolic and diastolic BP was very rapid in women, but completed within 15 to 30 s after assuming an upright position. Men increased BP at a much slower rate, but continued to produce higher BPs over the complete testing session (up to 15 min). The rate of change for men (15 mm Hg systolic and 10 mm Hg diastolic) was approximately half that for women (30 mm Hg systolic and 15 mm Hg diastolic) during the first 30 s of upright posture. However, after 60 s of standing, absolute change in systolic BP for the men exceeded that of the women by approximately 5 mm Hg for both systolic and diastolic BP. While men's heart rate remained relatively constant during standing, women compensated for the lower change in BP by a continual increase in heart rate throughout the duration of the test. Although both men and women demonstrated increases in norepinephrine at 5 and 15 min during standing, no difference between genders was observed. Similarly, there were no differences in dominant periodicity of heart rate during standing, although women demonstrated slightly higher beat-to-beat variation (RMS) than men. The results support the hypothesis of distributional differences in neuroeffector responses between men and women and have implications for how men and women respond to orthostatic stress across a variety of environmental conditions.Abstract
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There is growing evidence that free radicals mediated oxidative injury due to inadequate oxygen availability is an important factor in various pathologies at high altitude. Since vitamin E is known to protect the cells from oxidative damage due to its potent antioxidant properties, the present study was carried out to explore the effect of vitamin E supplementation on various hematological and biochemical parameters in hypoxia-induced oxidative stress in albino rats. The experiments were conducted on male albino rats by intermittently exposing them to a simulated altitude of 7576 m (25,000 ft), daily for 6 h for 15 d at 32 ± 2°C. The control group was fed vehicle only (1% Tween 80) and the experimental group was given vitamin E (40 mg per rat · d‒1) orally, 5 d prior to and during the period of hypoxic exposure. The variables studied include: hemoglobin, hematocrit, RBC deformability index, α-tocopherol level, malondialdehyde (MDA), reduced glutathione (GSH), oxidized glutathione (GSSG), lactate dehydrogenase (LDH) and protein level in blood/plasma and various tissues. Significant increase in hematocrit and hemoglobin and decrease in RBC deformability index was observed on exposure to hypoxia while vitamin E supplementation maintained them at the normal level. Hypoxia led to the decrease in plasma vitamin E and blood glutathione (GSH) level and two-fold increase in the plasma malondialdehyde (MDA) level. Vitamin E supplementation, on the other hand, resulted in less of an increase in MDA and increased the GSH concentration significantly. LDH activity, which was elevated on exposure to hypoxia, was arrested on vitamin E supplementation. The results indicate that vitamin E supplementation results in preventing oxidative damage due to high altitude stress.Abstract
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Oxygen uptake (V˙o2) on-kinetics is decelerated in acute hypoxia and accelerated in hyperoxia in comparison with normoxia during submaximal exercise. However, the effects of fraction of oxygen in inspired air (FiO2) on V˙o2 kinetics during maximal exercise are unknown. The effects of FiO2 on V˙o2 on-kinetics during maximal exercise are similar to submaximal exercise. There were 11 endurance athletes who were studied during maximal 7-min cycle ergometer exercise in hyperoxia (FiO2 0.325), hypoxia (FiO2 0.166) and normoxia (FiO2 0.209). The individual V˙o2 data were fit to a curve by using a three exponential model. In hypoxia, V˙o2 on-response amplitude during Phase 2 (~ 20-100 s from the beginning of exercise) was lower (p < 0.05) when compared with hyperoxia; time constant of V˙o2 Phase 3 (beyond ~ 100 s after beginning of exercise) was shorter (p < 0.05) when compared with hyperoxia; and mean response time (MRT, O-63%) for V˙o2 peak was shorter (p < 0.05) when compared with normoxia and hyperoxia. V˙o2 peak was higher in hyperoxia (4.80 ± 0.48 L · min−1, p < 0.05) and lower in hypoxia (4.03 ± 0.46 L · min−1, p < 0.05) than in normoxia (4.36 · 0.44 L · min−1). Moderate hypoxia or hyperoxia do not affect V˙o2 time constants at the onset of maximal exercise. However, MRT for V˙o2 peak is shortened in hypoxia. It is suggested that the differences in V˙o2 peak and power output during the latter half of the test and the point that FiO2 was modified only moderately might explain most of the discrepancy with the previous studies.Abstract
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Following a helicopter ditching in water, the survival rate of individuals not mortally injured by the impact ranges from 50-85%. One possible cause for this low survival rate is that the crew and passengers cannot hold their breath underwater long enough to make the often difficult escape from an inverted and submerged helicopter. We investigated pulmonary function, breath-holding times in air (BHTa) and water (BHTw) of 228 students enrolled in offshore survival courses required to work in either the offshore petroleum industry or in military marine aviation. Comparisons were performed based on occupation, SCUBA experience, and smoking. In 25°C pool water, the overall BHTw ranged from 5.4 to 120 s with a median of 37 s. Of the 228 subjects, 34% had a BHTw less than the 28 s required for the complete evacuation of a Super Puma helicopter under ideal conditions. No significant differences in BHTw were observed based on either smoking history (Non-Smoker, 41.5 ± 21.6 s; Smoker, 37.2 ± 20.2 s) or occupation (Novice, 37.5 ± 21.1 s; Offshore, 40.5 ± 21.1 s; Military, 45.2 ± 20.9 s). However, SCUBA-trained individuals had a significantly longer BHTw (47.4 ± 21.6 s) than non-SCUBA (37.6 ± 20.6 s), as well as a greater force vital capacity (FVC), BHTa, and subjective comfort in water. It is concluded that the inability to breath-hold in emergency situations is a major contributor to the low survival rates of marine helicopter ditchings. Therefore, efforts must be made to both decrease escape times and to increase survival time underwater.Abstract
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Although studies have been published regarding airline in-flight medical emergencies, there is a lack of any specific studies about in-flight psychiatric emergencies. This study seeks to ascertain the incidence of in-flight psychiatric emergencies, their associated factors, and outcomes. All in-flight calls for physician consultation to MedAire, a leading medical resource for airlines, during 1997 were reviewed for psychiatric symptomatology. Of 1375 consultations, 3.5% were characterized as psychiatric, with a large majority (90%) of these cases presenting primarily as acute anxiety. Most of the psychiatric cases (69%) required arrangements for the passenger to be evaluated on arrival, and three cases required emergency flight diversion and landing. This study suggests that an anxiolytic agent with a rapid onset may be indicated for the on-board medical kit.Abstract
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A 44-yr-old male pilot was diagnosed with non-ischemic cardiomyopathy, possibly as a complication of hereditary hemochromatosis, 8 yr after an acquired left bundle branch block was discovered on a routine ECG. Biochemical testing returned high levels of iron and percentage transferrin saturation, and genetic testing for hemochromatosis was remarkable for a heterozygous H63D mutation in the HFE gene on chromosome 6. Hereditary hemochromatosis should be considered in the differential diagnosis when a patient presents with cardiomyopathy and genetic testing for HFE gene variants influencing iron overload is now available as a clinical adjunct for diagnosis and patient management issues. Cardiomyopathy and symptomatic hemochromatosis are aeromedically disqualifying conditions in the U.S. Air Force; however, early identification of hereditary hemochromatosis susceptibility with biochemical or genetic diagnostic tests, followed by education in primary and secondary prevention, will prevent a significant proportion of the possible sequelae.Abstract
Halon 1301 and Halon 1211 are being replaced because they contribute to the depletion of ozone. Many of the potential candidate chemicals for replacing them are, like them, halogenated hydrocarbons. These chemicals have the potential to cause cardiac sensitization at high enough exposure concentrations. A physiologically based pharmacokinetic model, which mathematically describes the uptake, distribution, metabolism, and elimination of chemicals, was used to relate exposure to these chemicals with arterial blood concentrations resulting from the exposure. This information was then used to evaluate the potential for the occurrence of a cardiac-sensitizing event. The model was used to analyze the exposures to Halon 1301 and Halon 1211 in three aircraft (Navy E-2B, Cessna-421B, and Cessna-210C). Halon 1301 exposures were shown to be safe, but Haion 1211 resulted in arterial concentrations in exposed individuals that reached levels that could potentially cause cardiac sensitization. Use of the model for evaluating the risk from exposure to Halon 1301 and Halon 1211 is a moot point since both chemicals are being replaced. However, demonstration of the validity of the approach provides a tool for the evaluation of the health safety of replacement candidates. The National Fire Protection Association has approved use of this model for assessing times for safe egress from situations where agents are used to flood an area to extinguish a fire.Abstract
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Previous studies have revealed that female cabin attendants on long flights are most likely to have health problems. Since health problems can be related to workload and work stress and since the number of steps taken by an employee during a work shift can be an objective measure of the work load of cabin attendants, it is necessary to evaluate the predictors of the number of steps. We used pedometers worn by 118 female flight attendants to study the number of steps during flights and its predictors during long international flights. The mean number of steps during 636.53 (SD = 129.11)-minute flightw was 10,742.85 (SD = 3,547.17). The crude number of steps per minute was 16.88, and the adjusted number of steps per minute was 14.04. Flight length and the number of sleeping hours worked (i.e., between midnight and 6:00 am) were significant predictors of the number of steps. Although it is implied that flight duration and night flight increase the work load of flight attendants, we need to consider psychological aspects to evaluate the overall effects of their jobs on work stress and health.Abstract
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Aerospace medicine has evolved into a legitimate specialty through a long process of historical observation and technical achievement. However, most public literature on the topic has only covered information written through the late 1960s. This paper seeks to give a brief overview of the development of aerospace medicine and includes information about early advances in the field as well as more recent data. A MEDLINE search using “history,” “aerospace medicine,” and several other search terms as subject headings was the first step in gathering data. Also, personnel from the U.S. Air Force School of Aerospace Medicine library at Brooks AFB, TX, were consulted for current literature on the subject. From the earliest descriptions of mountain sickness, to the first manned balloon flight, and on to the invention of the airplane with man's forays into space, aerospace medicine has had a rich history. A great part of this rich history was contributed by pioneers, both past and present, of the U.S. Air Force.Abstract
In the foreseeable future, private companies will manufacture space vehicles with a capacity of transporting tourists into low Earth orbit. Because of the stresses of spaceflight, the effects of microgravity, and limited medical care capability, a system of medical clearance is highly recommended for these space tourists. It is our purpose to establish guidelines for use by private businesses, medical providers, and those planning on being a space tourist. Consequently, a Task Force was organized by the Aerospace Medical Association (ASMA) for the purpose of facilitating safety of passengers, fellow passengers, crew, and flight operations. The guidelines are meant to serve only as a template with the full expectation that exceptions might be made with appropriate rationale.Abstract
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