Damon AM, Lessley DJ, Salzar RS, Bass CR, Shen FH, Paskoff GR, Shender BS. Kinematic response of the spine during simulated aircraft ejections. Aviat Space Environ Med 2010; 81:453–9.Introduction: Military aviators are susceptible to spinal injuries during high-speed ejection scenarios. These injuries commonly arise as a result of strains induced by extreme flexion or compression of the spinal column. This study characterizes the vertebral motion of two postmortem human surrogates (PMHS) during a simulated catapult phase of ejection on a horizontal decelerator sled. Methods: During testing, the PMHS were restrained supinely to a mock ejection seat and subjected to a horizontal deceleration profile directed along the local z-axis. Two midsized males (175.3 cm, 77.1 kg; 185.4 cm, 72.6 kg) were tested. High-rate motion capture equipment was used to measure the three-dimensional displacement of the head, vertebrae, and pelvis during the ejection event. Results: The two PMHS showed generally similar kinematic motion. Head injury criterion (HIC) results were well below injury threshold levels for both specimens. The specimens both showed compression of the spine, with a reduction in length of 23.9 mm and 45.7 mm. Post-test autopsies revealed fractures in the C5, T1, and L1 vertebrae. Discussion: This paper provides an analysis of spinal motion during an aircraft ejection. The injuries observed in the test subjects were consistent with those seen in epidemiological studies. Future studies should examine the effects of gender, muscle tensing, out-of-position (of head from neutral position) occupants, and external forces (e.g., windblast) on spinal kinematics during aircraft ejection.

Cooper ES, Berry MP, McMurray RG, Hosick PA, Hackney AC. Core temperature influences on the relationship between exercise-induced leukocytosis and cortisol or TNF-α. Aviat Space Environ Med 2010; 81:460–6.Introduction: The extent to which exercise in the heat modifies leukocytosis and the relationship between the leukocytosis and tumor necrosis factor-alpha (TNF-α) or cortisol is not well understood. Thus, this study attempted to determine the combined effect of exercise and differing elevations in core temperature on exercise-induced leukocytosis and to examine associations between any leukocytosis and cortisol or TNF-α. Methods: Eight male subjects completed two 40-min trials while immersed in 25 and 38.5°C water. Leukocytes, TNF-α, and cortisol were determined at baseline, immediately post-, and 2 h post-exercise. Results: Both trials resulted in significant 13–33% increases in total leukocytes, mostly driven by a 24–30% increase in neutrophils. A significant relationship was found between the change in core temperature (T_re) during exercise and the increase in total leukocytes (r = 0.561). Similarly, the change in T_re was related to the change in cortisol (r = 0.557) and TNF-α (r = 0.483). Yet the exercise-induced change in cortisol was not significantly correlated to any changes in leukocytes. There was a trend for the relationships between the exercise-induced change in TNF-α and the changes in total leukocytes (r = 0.491) and neutrophils (r = 0.479). Discussion: These results suggest that although neither cortisol nor TNF-α are strong predictors of the leukocyte response during exercise or recovery, each factor may be one of many potential modifiers of the total leukocyte response.

Krog J, Tønnesen EK, Jepsen CF, Parner E, Segadal K, Hope A, Ulvik RJ, Hokland ME. Natural killer cells as biomarkers of hyperbaric stress during a dry heliox saturation dive. Aviat Space Environ Med 2010; 81:467–74.Introduction: Diving, hyperbaric oxygen, and decompression have been described as inducers of alterations in various components of the human immune system, such as the distribution of circulating lymphocytes. Hypothetically, the monitoring of specific lymphocyte subsets during hyperbaric exposure, including T- and NK-cell subsets, can serve as biomarkers of hyperbaric stress. Methods: Eight experienced saturation divers and eight reference subjects, naive to deep saturation diving, were examined. Peripheral blood mononuclear cells were isolated before and at different points during a 19.3-d dry heliox saturation dive to 2.64 MPa (254 msw). The NK cell cytotoxicity was estimated in a 4-h ⁵¹Cr-release assay using the NK cell sensitive tumor cell-line K562 as target cells. The major lymphocyte subpopulations, with special emphasis on the NK cell subsets, were phenotypically delineated by the use of 4-color flow cytometry. Results: Although NK cell cytotoxicity increased significantly in the divers during the compression phase and the reference subjects who remained in normoxic conditions outside the chamber, the NK cell cytotoxicity was significantly higher in the divers. Discussion: This finding, together with augmentation in the absolute number of circulating NK cells in the divers due to a possible activation of specific parts of the innate cellular immune system during hyperbaric exposure, suggests the monitoring of specific immune functions can be useful as biomarkers of hyperbaric-induced inflammatory stress.

Connolly DM. Spatial contrast sensitivity at twilight: luminance, monocularity, and oxygenation. Aviat Space Environ Med 2010; 81:475–83.Introduction: Visual performance in dim light is compromised by lack of oxygen (hypoxia). The possible influence of altered oxygenation on foveal contrast sensitivity under mesopic (twilight) viewing conditions is relevant to aircrew flying at night, including when using night vision devices, but is poorly documented. Methods: Foveal contrast sensitivity was measured binocularly and monocularly in 12 subjects at 7 spatial frequencies, ranging from 0.5 to ~16 cycles per degree, using sinusoidal Gabor patch gratings. Hypoxic performance breathing 14.1% oxygen, equivalent to altitude exposure at 3048 m (10,000 ft), was compared with breathing air at sea level (normoxia) at low photopic (28 cd · m⁻²), borderline upper mesopic (~2.1 cd · m⁻²) and midmesopic (~0.26 cd · m⁻²) luminance. Mesopic performance was also assessed breathing 100% oxygen (hyperoxia). Results: Typical ‘inverted U’ log/log plots of the contrast sensitivity function were obtained, with elevated thresholds (reduced sensitivity) at lower luminance. Binocular viewing enhanced sensitivity by a factor approximating √2 for most conditions, supporting neural summation of the contrast signal, but had greater influence at the lowest light level and highest spatial frequencies (8.26 and 16.51 cpd). Respiratory challenges had no effect. Conclusions: Contrast sensitivity is poorer when viewing monocularly and especially at midmesopic luminance, with relevance to night flying. The foveal contrast sensitivity function is unaffected by respiratory disturbance when twilight conditions favor cone vision, despite known effects on retinal illumination (pupil size). The resilience of the contrast sensitivity function belies the vulnerability of foveal low contrast acuity to mild hypoxia at mesopic luminance.

Dalecki M, Bock O, Guardiera S. Simulated flight path control of fighter pilots and novice subjects at +3 G_z in a human centrifuge. Aviat Space Environ Med 2010; 81:484-8.Background: We have previously shown that subjects produce exaggerated manual forces in +3 G_z. When subjects execute discrete flight path changes in a flight simulator, their performance is less stable in +3 G_z than in +1 G_z. Here we explore whether G_z-related deficits are found with continuous flight path changes. Methods: Novice subjects and fighter pilots sat in a high-fidelity flight simulator equipped with the reproduction of the Eurofighter 2000 cockpit, including the realistic flight stick, and pursued continuous altitude changes of a target airplane in +1 G_z and +3 G_z. Subjects also produced verbal responses in a Stroop task. Pursuit and Stroop tasks were administered alone and concurrently. Results: Flight instability increased in +3 G_z compared to +1 G_z in novices (+46%), but not in pilots (+3%), and even there only during the first minute. Flight performance improved after the first minute in both subject groups. Stroop reaction time was higher in novices (+5.27%) than in pilots (+3.77%) at +3 G_z. Dual-task costs did not differ between groups or G_z levels. Discussion: Deficits of force production in high G_z are largely compensated for when subjects apply forces to produce a continuously changing flight path. This compensation seems not to require additional cognitive resources and may be achieved by using visual feedback. Force production deficits in high G_z seem to have no appreciable effects on flight performance and cognitive load of experienced pilots using a force-plus-displacement stick in +3 G_z. It remains to be shown whether this conclusion extends to purely isometric sticks and to higher G_z levels.

Kennedy Q, Taylor JL, Reade G, Yesavage JA. Age and expertise effects in aviation decision making and flight control in a flight simulator. Aviat Space Environ Med 2010; 81:489-97.Introduction: Age (due to declines in cognitive abilities necessary for navigation) and level of aviation expertise are two factors that may affect aviation performance and decision making under adverse weather conditions. We examined the roles of age, expertise, and their relationship on aviation decision making and flight control performance during a flight simulator task. Methods: Seventy-two IFR-rated general aviators, aged 19–79 yr, made multiple approach, holding pattern entry, and landing decisions while navigating under Instrument Flight Rules weather conditions. Over three trials in which the fog level varied, subjects decided whether or not to land the aircraft. They also completed two holding pattern entries. Subjects' flight control during approaches and holding patterns was measured. Results: Older pilots (41+ yr) were more likely than younger pilots to land when visibility was inadequate (older pilots' mean false alarm rate: 0.44 vs 0.25). They also showed less precise flight control for components of the approach, performing 0.16 SD below mean approach scores. Expertise attenuated an age-related decline in flight control during holding patterns: older IFR/CFI performed 0.73 SD below mean score; younger IFR/CFI, younger CFII/ATP, older CFII/ATP: 0.32, 0.26, 0.03 SD above mean score. Additionally, pilots with faster processing speed (by median split) had a higher mean landing decision false alarm rate (0.42 vs 0.28), yet performed 0.14 SD above the mean approach control score. Conclusions: Results have implications regarding specialized training for older pilots and for understanding processes involved in older adults' real world decision making and performance.

Lomax M. Inspiratory muscle training, altitude, and arterial oxygen desaturation: a preliminary investigation. Aviat Space Environ Med 2010; 81:498–501.Introduction: Specific inspiratory muscle training (IMT) has been shown to significantly attenuate the fall in arterial oxygen saturation (S_po₂) during exhaustive exercise while breathing a hypoxic gas mixture of 14% oxygen. The aim of the current study was to assess the impact of IMT on resting S_po₂ over a range of altitudes in healthy individuals. Methods: Resting S_po₂ and the Borg Score were examined at altitudes of 0 or 400 m (0–400 m; 0–1312.3 ft), 1400 m, 4880 m, and 5550 m (4593 ft, 16,011 ft, and 18,209 ft) in 14 military personnel who were part of a climbing expedition to the Nepali Himalaya. Volunteer participants were randomly assigned to either a control (N = 7) or IMT (N = 7) group: IMT consisted of 1 set of 30 breaths twice daily at 50% maximal inspiratory mouth pressure (MIP) for 4 wk prior to departure. Results: MIP was similar between groups pre-IMT but increased significantly by 15% post-IMT. Baseline maximal expiratory mouth pressure was not different between groups. The Borg Score increased significantly from 1400 m, but was not different between groups at any altitude. Resting S_po₂ declined significantly at ascending altitudes in both groups and was similar between groups at altitudes of 0-400 m and 1400 m. However, at altitudes of 4880 m and 5550 m, S_po₂ was significantly higher (6%) in the IMT group. Conclusion: IMT can attenuate the fall in resting S_po₂, but only at altitudes of 4880 m and above. Conversely, IMT had no effect on resting levels of dyspnea as measured by the Borg Score.

Kass R, Kass J, Binder H, Kraft N. Conflict-handling mode scores of three crews before and after a 264-day spaceflight simulation. Aviat Space Environ Med 2010; 81:502–5.Introduction: In both the Russian and U.S. space programs, crew safety and mission success have at times been jeopardized by critical incidents related to psychological, behavioral, and interpersonal aspects of crew performance. The modes used for handling interpersonal conflict may play a key role in such situations. Methods: This study analyzed conflict-handling modes of three crews of four people each before and after a 264-d spaceflight simulation that was conducted in Russia in 1999–2000. Conflict was defined as a situation in which the concerns of two or more individuals appeared to be incompatible. Participants were assessed using the Thomas-Kilmann Conflict Mode Instrument, which uses 30 forced-choice items to produce scores for five modes of conflict handling. Results were compared to norms developed using managers at middle and upper levels of business and government. Results: Both before and after isolation, average scores for all crews were above 75% for Accommodating, below 25% for Collaborating, and within the middle 50% for Competing, Avoiding, and Compromising. Statistical analyses showed no significant difference between the crews and no statistically significant shift from pre- to post-isolation. Discussion: A crew predisposition to use Accommodating most and Collaborating least may be practical in experimental settings, but is less likely to be useful in resolving conflicts within or between crews on actual flights. Given that interpersonal conflicts exist in any environment, crews in future space missions might benefit from training in conflict management skills.

Summers RL, Martin DS, Platts SH, Mercado-Young R, Coleman TG, Kassemi M. Ventricular chamber sphericity during spaceflight and parabolic intervals of less than 1 G. Aviat Space Environ Med 2010; 81:506–10.Introduction: Pathology driven alterations in the geometric shape of the heart have been found to result in regional changes in ventricular wall stress and a remodeling of the myocardium. If reductions in the gravitational forces acting on the heart produce similar changes in the overall contour of the ventricles, this modification might also induce adaptations in the cardiac structure during long-term spaceflight. In this study we examined the changes in left ventricle (LV) shape in spaceflight and during parabolic flights. Methods: The diastole dimensions of the human LV were assessed with echocardiography during spaceflight and in parabolic flights which replicated the gravity of the Moon, Mars, and spaceflight and were compared to findings in Earth's gravity. LV dimensions were translated into circularity indices and geometric aspect ratios and correlated with their corresponding gravitational conditions. Results: During parabolic flight, a linear relationship (r = 0.99) was found between both the circularity index and geometric aspect ratio values and the respective gravitational fields in which they were measured. During spaceflight (N = 4) and parabolic flights (N = 3), there was an average 4.1 and 4.4% higher circularity index and a 5.3 and 8.1% lower geometric aspect ratio, respectively. Conclusions: A correlative trend was found between the degree of LV sphericity and the amount of gravitational force directed caudal to the longitudinal orientation of the body. The importance of this finding is uncertain, but may have implications regarding physiologic adaptations in the myocardial structure secondary to changes in LV wall stress upon prolonged exposure to microgravity.

Zeba I, Barkovic I, Knezevic S, Matanic-Lender D, Bralic M, Bulat-Kardum L. Pneumocephalus after an uneventful scuba dive. Aviat Space Environ Med 2010; 81:511–3.Scuba diving has become increasingly popular in the last 20 yr. Although it is considered safe, accidents, sometimes with fatal outcomes, do occur. The incidence of diving-related CNS barotrauma is low and it has been reported very infrequently. The clinical presentation may range from minimal dysesthesias to complete quadriplegia, encephalopathy, or death. In this paper we present a case of pneumocephalus in a 36-yr-old male scuba diver that presented with minor neurologic symptoms. A discussion, including a review of the literature, is also presented. The authors recommend that diving-induced neurologic dysbarism syndromes, including pneumocephalus, should be considered a possible cause when a scuba diver presents with neurologic symptoms, even minor ones.

Andrews JN, Weitzel EK, Eller R, McMains CK. Unsuccessful frontal balloon sinuplasty for recurrent sinus barotrauma. Aviat Space Environ Med 2010; 81:514–6.The standard of care treatment for diffuse recurrent sinus barotrauma (RSB) is an endoscopic sphenoethmoidectomy with a complete frontal dissection. Successful healing leaves the RSB patient with no ethmoid sinuses and endoscopically patent frontal, sphenoid, and maxillary ostia. In persistent cases, patients with small frontal ostia will go on to require a frontal drillout. Patients presenting for surgical management of RSB generally have minimal sinus disease despite significant symptoms during flight and the prospect of extensive surgical management can be unappealing. With the advent of balloon sinuplasty, military otolaryngologists anticipated this technology would permit therapeutic dilation of sinus ostia without the extensive surgical dissection and prolonged recovery typical for standard of care management. This case report is a cautionary note to the wider flight community to recognize a mechanism for recurrence of the underlying pathology when balloon sinuplasty is used that is not possible after properly performed standard of care sinus surgery for RSB.

Billings ce. Aviation medicine graduate training at Ohio State University, 1955-1977. Aviat Space Environ Med 2010; 81:517–21.Between 1955 and 1977, The Ohio State University sponsored what is believed to be the first residency training program in aviation medicine. The training program was instigated by Richard Meiling, M.D., the associate dean of the College of Medicine, who had been a U.S. Army flight surgeon during World War II. Dr. Meiling was active after the war in a committee of physicians that advocated establishment of a residency training program and certification of aviation medicine as an approved specialty. From 1955 to 1977, 51 physicians were trained at Ohio State in aviation (later aerospace) and occupational medicine. The programs were located in the Department of Preventive Medicine and directed by William F. Ashe, M.D., chairman. It was a 3-yr residency: the first was an academic year that included full-time coursework and research, and a second year was also devoted to advanced coursework and field experience, during which the resident finished conducting research and submitted a thesis. The third year was a practicum in which the residents were located at any of a number of academic, aeronautical, or industrial sites under supervision of faculty members. They were then qualified to take the examinations of the American Board of Preventive Medicine in either aviation or occupational medicine. A number of graduates took both examinations during the first years of practice following their training; several continued to practice in both specialties throughout their careers.

Williams M. You're the flight surgeon: flying phobia. Aviat Space Environ Med 2010; 81:527–8.

Schaefer HJ. Evaluation of present-day knowledge of cosmic radiation at extreme altitude in terms of the hazard to health. J Aviat Med 1950; 21: 375–418.