Hamilton DR, Murray JD, Ball CG. Cardiac health for astronauts: coronary calcification scores and CRP as criteria for selection and retention. Aviat Space Environ Med 2006; 77:377–387. Due to the limited treatment and return capabilities of most space vehicles, an in-flight cardiac event could result in significant mission impact or even failure. The current literature supports including electron-beam computed tomography (EBCT) and highly selective C-reactive protein (hsCRP) for diagnosis of coronary artery disease (CAD) in asymptomatic, low-pretest probability cohorts. This paper will examine the issues surrounding adding these tests to astronaut retention and selection algorithms. An evidenced-based literature review was performed and consensus obtained from subject-matter experts to create novel cardiac screening algorithms for astronaut applicants and the current astronaut corps. The main focus of this paper is to derive an evidenced-based approach for improving the diagnosis of significant CAD using EBCT and hsCRP testing. The recommended initial astronaut selection and long-duration mission assignment screening algorithms use EBCT-derived calcium scores and serum hsCRP levels to screen for CAD and predict individual cardiac risk. The current medical evidence is compelling for the international space medicine community to consider: 1.) Astronaut candidates with a coronary artery calcium score > 0 should be disqualified from initial selection; 2.) Astronauts with a coronary artery calcium score > 100 should be disqualified from selection for long-duration missions; 3.) Elevated hsCRP is a reliable risk factor for helping predict future cardiac events that should warrant primary prevention but not necessarily medical disqualification.

Smith SD, Smith JA. Head and helmet biodynamics and tracking performance in vibration environments. Aviat Space Environ Med 2006; 77:388–397. Introduction: There are potential effects of vibration on aircrew performance and safety when using helmet-mounted equipment. The objective of this study was to quantify the effects of head orientation and helmet center-of-gravity (CG) on head and helmet biodynamics and tracking performance during exposures to aircraft buffeting and quasi-random vibration. Methods: Three head orientations, including two off-axis or off-boresight configurations [Side (40° elevation, 70° azimuth) and Up (40° elevation, 0° azimuth)], and three helmet CGs were tested. The overall head, helmet, and helmet slippage displacement rotations, and rms tracking error and percent time-on-target were evaluated. Results: For both exposures, the two off-axis orientations produced significantly higher head, helmet, and slippage displacements; a relationship was observed between the orientation and the rotation that was affected (roll, pitch, or yaw). The highest slippage observed was in pitch in the forward (For) and Up orientations. Significantly higher performance degradation occurred with the Side orientation for two of the three CGs during aircraft buffeting, with minimal degradation observed with the quasi-random exposure. Higher head pitch and lower pitch slippage were associated with the CG estimated to produce loading behind the human head CG. Conclusions: The high off-boresight head movements may influence visual performance in operational vibration environments. Helmet instability appeared to be the greatest in pitch, which could have a significant effect on the design size of the exit pupil. The weight distribution or moments-of-inertia of the helmet system may also have a significant influence on both head/helmet biodynamics and tracking performance and should be investigated.

Wright HE, Cheung SS. Cranial-neck and inhalation rewarming failed to improve recovery from mild hypothermia. Aviat Space Environ Med 2006; 77:398403. Introduction: Rewarming from hypothermia in a field setting is a challenge due to the typical lack of significant power or heat source, making the targeted application of available heat critical. The highly vascular area of the head and neck may allow heat to be rapidly transferred to the core via blood circulation. At the same time, the warming of only a small skin surface may minimize the rapid rise in skin temperature proposed to attenuate shivering and endogenous heat production. Therefore, we investigated the efficacy of targeting the head and neck for rewarming from mild hypothermia. Methods: There were 16 participants (9 men, 24.1 ± 4.5 yr, 15.5 ± 3.9% body fat; 6 women, 23.0 ± 5.4 yr, 20.8 ± 3.2% body fat) who were cooled in 15°C water until rectal or esophageal temperature reached 35.5°C, whereupon they were removed and provided passive (PASS), cranial-neck (CN), or cranial-neck and inhalation (CNIR) rewarming. Heart rate and skin temperature were also measured. Results: The mean cooling times were PASS = 83 min (range: 22–295 min), CN = 94 min (range: 28–314 min), CNIR = 97 min (range: 22–285 min). No significant differences (p > 0.05) were found for magnitude of after-drop (PASS = 0.33 ± 0.24°C, CN = 0.31 ± 0.18°C, CNIR = 0.29 ± 0.28°C esophageal temperature) and duration of afterdrop (PASS = 15.4 ± 10.2 min, CN = 13.0 ± 10.1 min, CNIR = 8.8 ± 6.9 min). No significant differences (p > 0.05) were found for rewarming rate (PASS = 1.85 ± 1.33°C · h⁻¹, CN = 1.45 ± 1.04°C · h⁻¹, CNIR = 2.24 ± 1.51°C · h⁻¹ esophageal temperature). Discussion: In summary, neither cranial-neck nor cranial-neck and inhalation rewarming combined have an advantage in reducing the magnitude and duration of after-drop or increasing the rewarming rate over passive rewarming.

Shebilske WL, Tubré T, Tubré AH, Oman CM, Richards JT. Three-dimensional spatial skill training in a simulated space station: random vs. blocked designs. Aviat Space Environ Med 2006; 77:404–409. Background: Astronauts floating inside a spacecraft must be able to recall the direction to surrounding visual landmarks, regardless of their viewing perspective. If 3D orientation skills are taught preflight, should perspective sequences be blocked or randomized? Can standard spatial skill tests predict performance? Methods: Undergraduates (40 men and 40 women; ages 19–24) learned 3D spatial relationships among landmark pictures in a cubic chamber simulating a space station node. Subjects learned to predict picture directions when told one picture’s direction (the one behind them) and the subject’s simulated roll orientation, which was changed between trials by rotating pictures. The dependent variable was the proportion of correct predictions. A between group (n = 40 per group) independent variable was training type (random vs. blocked sequencing of perspectives). Experiment phase (familiarization, training, transfer, and 2 retention phases) was a within group variable. Subjects also took three standard spatial skill tests: Card Rotation, Cube Comparison, and Group Imbedded Figures. Results: As hypothesized, during training, performance for the random group (0.56) was worse than the blocked group (0.83); during transfer, the random group (0.75) was better than the blocked group (0.56); during retention-1, the random group (0.70) was better than the blocked group (0.55); and during retention-2, the random group (0.76) was better than the blocked group (0.65). Spatial skill tests correlated differently across the two groups, indicating that random sequencing elicits different skills. Conclusion: Random presentation enhances 3D spatial skill transfer and retention. Standard spatial tests can predict performance and have the potential to customize training.

Otsuka Y, Onozawa A, Miyamoto Y. Hormonal responses of pilots to training flights: the effects of experience on apparent stress. Aviat Space Environ Med 2006; 77:410–414. Introduction: The levels of urinary noradrenaline (NAd), adrenaline (Ad) and salivary cortisol (Cor) were determined in student and instructor pilots during Phase 1 (training with propeller engine; PH1), and Phase 2 (training with jet engine; PH2) flight training. Methods: The subjects in PH1 were 30 students and 33 instructors, and in PH2 were 17 students and 15 instructors. Urine and saliva were collected approximately 30 min before and 20 min after the flights. The ratio (post/pre-flight) of the hormonal levels was calculated to compare the students with the instructors and/or PH1 with PH2. Results: In PH1, the levels of all three hormones for postflight were significantly higher than for preflight in students, and the ratios of all three hormones in students were significantly higher than in instructors. In PH2, the ratios of all three hormones for students and instructors did not differ significantly, and the ratios of Ad and Cor levels in students for PH2 were significantly lower than for PH1 (Ad: 1.64 ± 0.10 vs. 2.23 ± 0.14; Cor: 0.86 ± 0.16 vs. 1.68 ± 0.11, respectively). Conclusions: The results from PH1 clearly demonstrated that flight stress for students was significantly higher than for instructors. The ratios might be regarded as result of adaptation to flight stress in students. We conclude that the ratios of Ad and Cor levels are a good indicator of stress coping in student pilots.

Wallace RF, Kriebel D, Punnett L, Wegman DH, Wenger CB, Gardner JW, Kark JA. Risk factors for recruit exertional heat illness by gender and training period. Aviat Space Environ Med 2006; 77:415–421. Introduction: Exertional heat illness (EHI) is a recurrent problem for both male and female recruits during basic military training. A matched case control study investigated the effects of fitness and conditioning on EHI risk among Marine Corps recruits during 12 wk of basic training at Marine Corps Recruit Depot, Parris Island, SC. Methods: Physical fitness and anthropometric measurements at entrance were acquired for 627 EHI cases that occurred during the period 1988–1996 and for 1802 controls drawn from the same training platoons. Conditional logistic regression was used to estimate EHI risk. Results: Slower physical fitness test run times during processing week strongly predicted risk for subsequent EHI in both male and female recruits. A 9% increase in risk for EHI associated with body mass index (BMI = kg · m⁻²; weight/height²) was found in male recruits, while BMI was not associated with risk among female recruits. BMI and initial run time were important predictors for EHI in early training, while in late training the initial BMI was no longer as important a risk factor and improvements in fitness reduced risk. Conclusion: Tables of estimated absolute risks categorized by BMI and [V-dot]o₂max are provided as a guide for identifying recruits who are at high risk for developing EHI during training.

Martinussen M, Richardsen AM. Air traffic controller burnout: survey responses regarding job demands, job resources, and health. Aviat Space Environ Med 2006; 77:422–428. Introduction: There are currently many changes taking place in the aviation system affecting the work of air traffic controllers (ATCOs), and thus it was considered important to assess work-related demands and stress responses among ATCOs. The purpose of this study was to assess the level of burnout among ATCOs compared with other professions; to examine the relationship between job demands, job resources, and burnout; and to examine if burnout could predict both work- and health-related outcomes. Method: The participants were 209 Norwegian ATCOs and data were collected using a questionnaire distributed to 500 ATCOs. The study was part of a national survey of both health care and non-health care professions. Results: ATCOs did not score high on burnout compared with the three comparisons groups (police, journalists, and building constructors); in fact, ATCOs scored significantly lower on exhaustion compared with journalists (Hedges g = 65) and building constructors (Hedges g = 63), and not significantly different from police officers. Both job demands and job resources were related to burnout; work conflict especially was an important predictor for all of the three burnout dimensions. Burnout predicted psychosomatic complaints (r² = 0.48), satisfaction with life (r² = 0.25), and other work outcomes. Discussion: The overall level of burnout was not high among ATCOs compared with other professions, which may be related to selection procedures for the profession. Burnout was related to important outcome variables such as psychosomatic complaints and attitudes toward work.

Platts SH, Ziegler MG, Waters WW, Meck JV. Hemodynamic effects of midodrine after spaceflight in astronauts without orthostatic hypotension. Aviat Space Environ Med 2006; 77:429–433. Introduction: Orthostatic hypotension and presyncope are common and potentially serious risks for astronauts returning from space. Susceptible subjects fail to generate an adequate adrenergic response to upright posture. The α-1 adrenergic agonist, midodrine, may be an effective countermeasure. We tested the hypothesis that midodrine would have no negative hemodynamic effect on healthy astronauts returning from space. Methods: Five male astronauts participated in preflight and postflight tilt testing on a control flight as well as on the test flights, where midodrine (10 mg, orally) was administered after landing ∼1 h before testing. Results: None of these astronauts exhibited orthostatic hypotension or presyncope before or after either flight. Midodrine did not cause any untoward reactions in these subjects before or after flight; in fact, a modest beneficial effect was seen on postflight tachycardia (p = 0.036). Discussion: These data show that midodrine protected against post-spaceflight increases in heart rate without having any adverse hemodynamic effects on non-presyncopal, male astronauts. Among these subjects, midodrine was a safe cardiovascular countermeasure.

John-Baptiste A, Cook T, Straus S, Naglie G, Gray G, Tomlinson G, Krahn M. Decision analysis in aerospace medicine: costs and benefits of a hyperbaric facility in space. Aviat Space Environ Med 2006; 77:434–443. Introduction: Assembly and maintenance of the International Space Station (ISS) requires an unprecedented number of spacewalks, which expose astronauts to the risk of decompression sickness (DCS). We illustrate the use of decision analysis to compare a hyperbaric oxygen (HBO) chamber to currently available therapy for DCS treatment on the ISS. Methods: A decision-analytic model that simulates events over the lifespan of the ISS was constructed. Inputs to the model for probabilities, costs, and measures of morbidity and mortality were derived from a variety of sources, including a systematic literature review and an iterative consultation process with personnel at the Canadian Space Agency and the National Aeronautics and Space Administration (NASA). The decision model was analyzed using the methods of Monte-Carlo simulation and expected value calculation. Main outcome measures included the present value of costs and quality adjusted life years (QALYs), and the cumulative probability of mission-related events over the life cycle of the ISS. Sensitivity analysis was performed. Results: The HBO chamber strategy is associated with a mean cost of −$12.5 million (a net cost saving of $12.5 million) with a 95% CI (−$112.8 million, $51.3 million). An HBO chamber reduces the likelihood of a premature shuttle return and a premature Soyuz return by 8% and 3%, respectively. The result is sensitive to the lifespan of the ISS. Conclusions: At a $50 million cost, an HBO chamber is likely, though not certain, to result in cost savings. Decision analysis is a useful tool for use in priority setting in aerospace medicine.

Huber SW. Recovery from unusual attitudes: HUD vs. back-up display in a static F/A-18 simulator. Aviat Space Environ Med 2006; 77:444–448. Objective: Spatial disorientation (SD) remains one of the most important causes of fatal fighter aircraft accidents. The aim of this study was to give a recommendation for the use of the head-up display (HUD) or back-up attitude directional indicator (ADI) in a state of spatial disorientation based on the respective performance in an unusual attitude recovery task. Methods: Seven fighter pilots joining a conversion course to the F/A-18 participated in this study. Flight time will be presented as range (and mean in parentheses). Total military flight experience of the subjects was 835–1759 h (1412 h). Flight time on the F/A-18 was 41–123 h (70 h). The study was performed in a fixed base F/A-18D Weapons Tactics Trainer. We tested the recovery from 11 unusual attitudes and analyzed decision time (DT), total recovery time (TRT), and error rates for the HUD or the back-up ADI. Results: We found no differences regarding either reaction times or error rates. For the HUD we found a DT (mean ± SD) of 1.3 ± 0.4 s, a TRT of 9.1 ± 4.1 s, and an error rate of 29%. For the ADI the respective values were a DT of 1.4 ± 0.4 s, a TRT of 8.3 ± 3.8 s, and an error rate of 27%. Conclusion: Unusual attitude recoveries are performed equally well using the HUD or the back-up ADI. Switching from one instrument to the other during recovery should be avoided since it would probably result in a loss of time without benefit.

Fuglesang C, Narici L, Picozza P, Sannita WG. Phosphenes in low Earth orbit: survey responses from 59 astronauts. Aviat Space Environ Med 2006; 77:449–452. Introduction: It has long been known that many people in space experience sudden phosphenes, or light flashes. Although it is clear that they are related to high-energy particles in the space radiation environment, many details about them are still unknown. In an effort to gain more knowledge about the light flashes, a study was initiated to collect information from people who have recently flown in space. Method: A survey conducted by anonymous questionnaire was performed among astronauts regarding their experience of sudden light flashes in space. In all, 98 surveys were distributed to current NASA and ESA astronauts. Results: Among the 59 respondents, 47 noticed them sometime during spaceflight. Most often they were noted before sleep, and several people even thought the light flashes disturbed their sleep. The light flashes predominantly appear white, have elongated shapes, and most interestingly, often come with a sense of motion. The motion is described as sideways, diagonal, or in-out, but never in the vertical direction. Discussion: Comparisons with earlier studies of light flashes in space and several ground-based studies during the 1970s are made. One interesting observation from this is that it seems that a small fraction of the light flashes is caused by Cherenkov radiation, while the majority is probably caused by some kind of direct interaction with elements in the retina.

Russomano T, Evetts SN, Castro J, dos Santos MA, Gavillon J, Azevedo DFG, Whittle J, Coats E, Ernsting J. A device for sampling arterialized earlobe blood in austere environments. Aviat Space Environ Med 2006; 77:453–455. Introduction: There is currently no effective method of measuring arterial blood gas tensions in austere environments such as in space or at high altitude. An alternative to direct arterial measurement is the sampling of arterialized earlobe blood, an accurate technique that has been in use in clinical medicine and physiology for more than 50 yr. We, therefore, developed an earlobe arterialized blood (EAB) collector for practical use in extreme environments. Methods: The results from the EAB collector were compared with simultaneous samples of blood drawn from the radial artery. Six healthy subjects breathed a gas mixture of 12.8% O₂ in N₂ during 15 min of 8° head-down tilt. The blood samples were analyzed immediately. Results: The mean differences in Po₂ between arterialized earlobe and radial artery samples were 0.25 ± 1.25 mmHg for Po₂ and 1.0 ± 0.75 mmHg for Pco₂; neither difference was significant. There was no difference between the pH values obtained by the two techniques. Conclusion: This study suggests that arterialized blood sampled from the earlobe using the EAB collector may provide sufficiently accurate measurements of the Po₂, Pco₂ and pH of arterial blood for clinical or research use in extreme environments.

Heller SR, Nicholson AN. Aircrew and type 1 diabetes mellitus. Aviat Space Environ Med 2006; 77:456–458. The most stringent clinical criteria cannot guarantee that individuals with Type 1 diabetes mellitus (DM) will preserve awareness of an impending hypoglycemic episode or that a hypoglycemic episode can be prevented. Further, cognition may be impaired for a considerable period of time beyond the correction of any episode. These observations and their implications to operational aircrew with Type 1 DM are discussed.

Carter D, Pokroy R, Barenboim E, Azaria B, Goldstein L. Apical hypertrophic cardiomyopathy and arrhythmia in military pilots. Aviat Space Environ Med 2006; 77:459–461. Apical hypertrophic cardiomyopathy (ApHCM), a subtype of hypertrophic cardiomyopathy, may be found incidentally in healthy young adults. Arrhythmias are poor prognostic signs, and are the most frequent cause of sudden cardiac death. We present two cases of military aviators with ApHCM. One was a high-performance jet weapon system operator, who had asymptomatic non-sustained ventricular tachycardia (NSVT) and subsequently a symptomatic episode of paroxysmal atrial fibrillation. The second was a helicopter pilot, who had asymptomatic NSVT. Both aviators continue their aviation duties without exposure to +Gz under a regime of regular thorough cardiac assessment.