Cultural and personal traits will become important as the number of short-duration spaceflights of international crews supporting the International Space Station (ISS) increases and more people begin staying aboard ISS for longer durations. This project investigated the interpersonal and personal changes of Japanese subjects during a 1 -wk stay in the Japanese Experiment Module. The Gieβen Test (GT) was used to determine if the cultural background and personality traits of the subjects become more explicit and stronger during isolation. Six males and two females aged 22-28 yr participated in the study. They stayed 7 d in the isolation chamber at the National Space Development Agency of Japan (NASDA). The GT was chosen as an individual and group diagnostic instrument; it was administrated four times during, and one time after, isolation. According to the GT-self-picture, subjects exhibited a change toward negative social resonance and social withdrawal. Subgroups formed but caused no isolation or tension. The GT-foreign-pictures showed that the judgment of other subjects changed toward hedonic and permeability directions. The common interpersonal relationships of the Japanese subjects influenced the group dynamics. These relationships tend to be integrative and tend to support the network and value systems, emphasizing connectedness and minimizing differences. The cultural background became more explicit and stronger during isolation. Based on this, isolation studies with international crews and intercultural training will be necessary for international crews performing both short- and long-duration missions.Abstract
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A randomized, single-blind, controlled trial was carried out to: 1) examine the safety of patients flying on commercial airlines 2 wk after a myocardial infarction; 2) determine whether or not the use of supplemental oxygen was associated with a reduced risk of in-flight adverse events; and 3) determine the need for a medical escort. There were 38 patients who were prospectively and randomly assigned supplemental continuous oxygen therapy (2 L · min-1 via nasal prongs; n = 19) or no oxygen (n = 19) during the flight. Prior to flying, an escorting doctor completed a medical questionnaire for each patient. Both groups underwent Holter monitoring throughout the flight. The major end-point was the development of inflight myocardial ischemia, as detected by Holter monitoring. Minor end-points included patients complaining of chest pain or dyspnea; the detection of bigeminy or trigeminy by Holter monitoring; or oxygen desaturation to less than 90%, as measured by pulse oximetry. Of the 38 patients enrolled, there was only 1 major end-point. This patient had a brief, self-limiting, asymptomatic episode of myocardial ischemia diagnosed by Holter monitoring. Minor end-points occurred in 13 (34%) patients. One patient had asymptomatic evidence of S-T depression on a transport monitor, but not on the Holter. Five patients had transient low (<90%) oxygen saturations, two complained of chest pain, and five had complex ventricular ectopic beats or periods of transient ventricular tachycardia. None of the minor end-points were associated with Holter evidence of myocardial ischemia. Of the 30 patients with completed questionnaires and Holter results, there was no difference in the incidence of minor end-points between the oxygen (5/13) and no oxygen groups (6/15) (p = 0.93). Intervention by the medical escort consisted of commencing oxygen therapy on those patients with low oxygen saturations and those with chest pain. Use of an already dispensed glyceryl trinitrate spray was initiated in one patient with chest pain that turned out to be non-ischemic when the Holter traces were later analyzed. This study suggests that, provided that care is taken during the immediate preflight and postflight phases not to overexert the patients, neither supplemental oxygen nor medical escorts are needed in the transportation of patients who fly 2 wk after acute myocardial infarction.Abstract
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Previous studies have indicated that, compared with nonpilots, pilots rely more on vision than "seat-of-the-pants" sensations when presented with visual-vestibular conflict. The objective of this study was to evaluate whether pilots and nonpilots differ in their thresholds for tilt perception while viewing visual scenes depicting simulated flight. This study was conducted in the Advanced Spatial Disorientation Demonstrator (ASDD) at Brooks AFB, TX. There were 14 subjects (7 pilots and 7 nonpilots) who recorded tilt detection thresholds in pitch and roll while exposed to sub-threshold movement in each axis. During each test run, subjects were presented with computer-generated visual scenes depicting accelerating forward flight by day or night, and a blank (control) condition. The only significant effect detected by an analysis of variance (ANOVA) was that all subjects were more sensitive to tilt in roll than in pitch [F (2,24) = 18.96, p < 0.001]. Overall, pilots had marginally higher tilt detection thresholds compared with nonpilots (p = 0.055), but the type of visual scene had no significant effect on thresholds. In this study, pilots did not demonstrate greater visual dominance over vestibular and proprioceptive cues than nonpilots, but appeared to have higher pitch and roll thresholds overall. The finding of significantly lower detection thresholds in the roll axis vs. the pitch axis was an incidental finding for both subject groups.Abstract
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Spatial disorientation (SD) refers to pilots' inability to accurately interpret the attitude of their aircraft with respect to Earth. Unfortunately, SD statistics have held constant for the past few decades, through the transition from the head-down attitude indicator (AI) to the head-up display (HUD) as the attitude instrument. The newest attitudeindicating device to find its way into military cockpits is the helmetmounted display (HMD). HMDs were initially introduced into the cockpit to enhance target location and weapon-pointing, but there is currently an effort to make HMDs attitude reference displays so pilots need not go head-down to obtain attitude information. However, unintuitive information or inappropriate implementation of on-boresight attitude symbology on the HMD may contribute to the SD problem. The occurrence of control reversal errors (CREs) during unusual attitude recovery tasks when using an HMD to provide attitude information was investigated. The effect of such errors was evaluated in terms of altitude changes during recovery and time to recover. There were 12 pilot-subjects who completed 8 unusual attitude recovery tasks. Results showed that CREs did occur, and there was a significant negative effect of these errors on absolute altitude change, but not on total recovery time. Results failed to show a decrease in the number of CREs occurring when using the HMD as compared with data from other studies that used an AI or a HUD. Results suggest that new HMD attitude symbology needs to be designed to help reduce CREs and, perhaps, SD incidences.Abstract
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In order to investigate the effects of simulated weightlessness on drug metabolism, liver, kidney, and small intestine, microsomal proteins from tail-suspended rats were analyzed to determine cytochrome P450 (CYP) and P-glycoprotein levels following varying durations of tail-suspension. P-glycoprotein and CYP levels would both decrease similar to previous findings from actual spaceflight data. Six groups of four Sprague-Dawley rats each were tail-suspended for up to 21 d; CYP and P-glycoprotein levels in the liver, kidney and small intestine were then measured by Western blotting. The results were compared with a control group of unsuspended rats. Our data showed there were significant changes in the levels of hepatic CYP2CI 1,2E1,4A1, and P-glycoprotein and significant changes in the levels of P-glycoprotein and CYP4A1 in the kidney. However, there were no significant changes detected in the levels of CYP3A2 in the liver or small intestine. We conclude that simulated weightlessness, using the tail-suspended rat model, showed significant suppressive effects on levels of CYP2C11,2 El, and P-glycoprotein in the liver and CYP4A1 in the kidney, while demonstrating no significant effect on the levels of CYP3A2 in the liver or small intestine. Thus, generalized predictions on the effect of simulated microgravity on drug metabolism cannot be made and the overall effect of spaceflight on individual enzymes should be investigated.Abstract
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The effect of vibration stimulation on muscular strength is an emerging field of research and very little comprehensive work has been conducted at this stage. There will be no effects of timing or application of vibration stimulation on muscular strength and activation across isometric, isokinetic and concentric isotonic contractions. There were 28 recreational athletes who participated in this study. Their characteristics were: (mean ± SD) age, 22.8 ± 5.6 yr; height, 174.1 ± 8.8 cm; and body mass, 78.0 ± 13.6 kg. The vibration stimulation was delivered at 50.42 ± 1.16 Hz with an acceleration of 13.24 ± 0.18 ms–2. A series of one-way ANOVAs revealed significant (p < 0.05) improvements of 14.7 ± 2.9% and 15.3 ± 3.1% above normal contraction levels for concentric isotonic strength during and after the vibration stimulation, respectively. No significant improvements in isometric and isokinetic strength were evident. Concurrent measurement of electromyography (EMG) presented significant improvements during stimulation of 30.1 ± 14.6%, 43.0 ± 13.0%, and 107.1 ± 44.4% in mean activation of rectus femoris (RF) for the isometric, isokinetic, and concentric isotonic contractions, respectively. Synchronous collection of vibromyography (VMG) during stimulation displayed a significant decrease of -6.4 ± 1.5%, -5.1 ± 1.2%, and -4.1 ± 1.7% in mean VMG activity of RF for the isometric, isokinetic, and concentric isotonic contractions, respectively. Significant improvements in muscular strength and activation for concentric isotonic contractions performed during an applied vibration suggest that the optimal timing of a vibratory stimulation would be while the participant is contracting isotonically. However, further research needs to be conducted to establish the exact mechanism behind these improvements.Abstract
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Decompression to simulated altitude causes super-saturation of nitrogen desolved in body tissues and can result in venous gas emboli (VGE), which are usually "cleared" in the lung. Large intravenous boli of air administered to animals increase pulmonary artery pressure (PAP), and may induce cross-over of gas to the left side of the heart (creating dangerous arterial gas emboli). This study was conducted to determine whether high VGE grades induced at simulated altitude elevate PAP in humans. Eight human subjects with subclinical tricuspid regurgitation were exposed to simulated altitude of ≥ 24,000 ft (7315 m) for up to 4 h. Systolic PAP was derived from Doppler ultrasound echo imaging measurements of peak flow velocity of the regurgitant jet. VGE was rated using the Spencer scale. A technique of “bubble titration” was employed with changes in exercise and altitude to maintain sufficient bubbles without decompression sickness. All subjects developed grade III-IV VGE, but 3 developed decompression sickness, resulting in earlier termination. Pre-exposure systolic PAP averaged 24.4 ± 1.3 (SE) mm Hg. After 1,2, 3 and 4 h, systolic PAP was 23.7 ± 1.2 (n = 8), 23.4 ± 1.1 (n = 8), 23.3± 1.0 (n = 6), and 25.9 ± 0.6 (n = 5) mm Hg, respectively. Systolic PAP remained unchanged, in spite of bubble grades III-IV for up to 4 h As systolic PAP did not increase with hypobaric exposures that created substantial VGE, the bubble loading was not sufficient to overwhelm the lung clearing capacity. The risk of high PAP resulting in VGE cross-over is low during typical operational altitude exposures.Abstract
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Pilot errors are recognized as a contributing factor in as many as 80% of aviation crashes. Experimental studies using flight simulators indicate that due to decreased working memory capacity, older pilots are outperformed by their younger counterparts in communication tasks and flight summary scores. This study examines age-related differences in crash circumstances and pilot errors in a sample of pilots who flew commuter aircraft or air taxis and who were involved in airplane or helicopter crashes. A historical cohort of 3306 pilots who in 1987 flew commuter aircraft or air taxis and were 45-54 yr of age was constructed using the Federal Aviation Administration's airmen information system. Crash records of the study subjects for the years 1983-1997 were obtained from the National Transportation Safety Board (NTSB) by matching name and date of birth. NTSB's investigation reports were reviewed to identify pilot errors and other contributing factors. Comparisons of crash circumstances and human factors were made between pilots aged 40-49 yr and pilots aged 50-63 yr. A total of 165 crash records were studied, with 52% of these crashes involving pilots aged 50-63 yr. Crash circumstances, such as time and location of crash, type and phase of flight, and weather conditions, were similar between the two age groups. Pilot error was a contributing factor in 73% of the crashes involving younger pilots and in 69% of the crashes involving older pilots (p = 0.50). Age-related differences in the pattern of pilot errors were statistically insignificant. Overall, 23% of pilot errors were attributable to inattentiveness, 20% to flawed decisions, 18% to mishandled aircraft kinetics, and 18% to mishandled wind/runway conditions. Neither crash circumstances nor the prevalence and patterns of pilot errors appear to change significantly as age increases from the 40s to the 50s and early 60s.Abstract
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Pulmonary barotrauma-induced cerebral arterial gas embolism (CAGE) continues to complicate compressed gas diving activities. Inadequate lung ventilation secondary to inadvertent breath holding or rapid buoyant ascent can quickly generate a critical state of lung over-pressure. Pulmonary over-pressurization may also occur as a consequence of acute and chronic pulmonary pathologies. Resulting barotrauma frequently causes structural failure within the terminal distal airway. Respiratory gases are then free to embolize the systemic circulation via the pulmonary vasculature and the left heart. The brain is a common target organ. Bubbles that enter the cerebral arteries coalesce to form columns of gas as the vascular network narrows. Small amounts of gas frequently pass directly through the cerebral circulation without occlusion. Larger columns of gas occlude regional brain blood flow, either transiently or permanently, producing a stroke-like clinical picture. In cases of spontaneous redistribution, a period of apparent recovery is frequently followed by relapse. The etiology of relapse appears to be multifactoral, and chiefly the consequence of a failure of reperfusion. Prediction of who will relapse is not possible, and any such relapse is of ominous prognostic significance. It is advisable, therefore, that CAGE patients who undergo spontaneous recovery be promptly recompressed while breathing oxygen. Therapeutic compression will serve to antagonize leukocyte-mediated ischemia-reperfusion injury; limit potential reembolization of brain blood flow, secondary to further leakage from the original pulmonary lesion or recirculation of gas from the initial occlusive event; protect against embolic injury to other organs; aid in the resolution of component cerebral edema; reduce the likelihood of late brain infarction reported in patients who have undergone spontaneous clinical recovery; and prophylax against decompression sickness in high gas loading dives that precede accelerated ascents and omitted stage decompression.Abstract
As the Russian Space Agency and the U.S. National Aeronautics and Space Administration began in the mid-1990s to plan a preliminary cooperative flight program in anticipation of the International Space Station, programmatic and philosophical differences became apparent in the technical and medical approaches of the two agencies. This paper briefly describes some of these differences and the process by which the two sides resolved differences in their approaches to the medical selection and certification of NASA-Mir crewmembers. These negotiations formed the basis for developing policies on other aspects of the medical support function for international missions, including crew training, preflight and postflight data collection, and rehabilitation protocols. The experience gained through this cooperative effort has been invaluable for developing medical care capabilities for the International Space Station.Abstract