Kim S-H, Prinzel LJ, Kaber DB, Alexander AL, Stelzer EM, Kaufmann K, Veil T. Multidimensional measure of display clutter and pilot performance for advanced head-up display. Aviat Space Environ Med 2011; 82:1013–22.Introduction: This study was conducted to: develop a multidimensional measure of display clutter for advanced head-up displays (HUDs) incorporating enhanced and synthetic vision; assess the influence of HUD configuration on perceptions of display clutter, workload, and flight performance; model clutter scores in terms of visual display properties; and model flight performance in terms of subjective and objective clutter indices. Methods: In a flight simulator, 18 pilots with different levels of flight experience flew approaches divided into three segments. Three HUD configuration sets were presented under two levels of flight workload. Pilot ratings of overall display clutter, its underlying dimensions, and mental workload were recorded along with flight performance measures. Display image analysis software was used to measure visual properties of the HUDs. Results: The multidimensional measure of clutter showed internal consistency with overall perceived clutter. Calculated clutter scores were sensitive to HUD configurations and in agreement with a priori display classifications. There was a trend for the extremes of display clutter to cause higher workload and less stable performance due to cognitive complexity and a lack of information for high and low clutter displays, respectively. Multiple linear regression models of perceived clutter were developed based on HUD visual properties with predictive utility. Models of flight performance based on the clutter score and workload ratings were also developed, but with less predictive power. Discussion: Measures and models of display clutter are expected to be applicable to the evaluation of a range of display concepts.

Keshavarz B, Hecht H. Axis rotation and visually induced motion sickness: the role of combined roll, pitch, and yaw motion. Aviat Space Environ Med 2011; 82:1023–9.Background: Motion sickness (MS) is a well-known phenomenon in aviation and in virtual environments such as simulators or computer games. The severity of MS is thought to be due to the amount of sensory conflict, which should increase with the complexity of the simulated motion. The present study focused on the direction and complexity of simulated body rotations in the genesis and severity of visually induced MS. Methods: Three simulated rollercoaster rides including translational movement in the fore-aft axis and additional rotational motion either in pitch only, along the pitch and roll axes, or in pitch, roll, and yaw were generated. We presented video clips of 15 min on a large projection screen to a total number of 61 volunteers, who were randomly assigned to 1 of the 3 rotational motion groups. MS was measured using the Fast Motion Sickness Scale (20-point verbal rating scale) and the Simulator Sickness Questionnaire. Aftereffects were captured up to 5 h after the experiment was finished. Results: Analyses indicated lowest MS scores in the pitch-only condition (1.95). Dual- (4.33) or triple-axis (5.30) combinations revealed significantly higher MS scores than the single-axis condition, but surprisingly did not differ from each other. MS started to subside rapidly after about 1 h past stimulus presentation. Discussion: We conclude that the complexity of visual motion does not increase MS linearly. Instead, we propose that MS reached a plateau in the dual-axis condition and adding a third rotational axis did not further surpass the severity of MS reached.

Maruyama S, Kemuriyama T, Manabe T, Takahata T, Shoji I, Nishida Y. Severe hypotension during the decreasing phase of G_z stress in anesthetized rats wearing an anti-G suit. Aviat Space Environ Med 2011; 82:1030–6.Introduction: Physiological responses to +G_z stress have been reported in several studies. However, no reports exist on differences in arterial pressure responses between increasing and decreasing G phases. We hypothesized that +G_z stress and/or an anti-G support might disturb the circulation system and cause potential brain hypoperfusion, even if the anti-G support protects against G-induced loss of consciousness. Methods: Dependency of +G_z magnitude, hemodynamic changes, renal sympathetic nerve activity (RSNA), and aortic blood flow (AoBF) were estimated in anesthetized rats to analyze the effects of +G_z stress and/or an anti-G support on arterial pressure at a level of the brain (APLB). The rats were exposed to +G_z using a centrifuge for small animals while wearing an anti-G suit. Results: APLB remained at the control level while the anti-G suit was inflated. However, a decrease in APLB was observed twice during increasing and decreasing G phases using the anti-G suit. Hypotension in the decreasing G phase at +5 G_z was significantly deeper than that in the increasing G phase (47.5 ± 7.7 vs. 29.6 ± 3.0 mmHg). RSNA responses to G_z loads were greater in the decreasing G than in the increasing G phase (129.7 ± 8.6 vs. 147.3 ± 10.4%). Both AoBF and calculated vascular resistance were suppressed more significantly in the decreasing G than in the increasing G phase (38.3 ± 4.4 vs. 34.4 ± 3.4 ml · min⁻¹, 1.44 ± 0.22 vs. 1.09 ± 0.14 mmHg · min⁻¹ · ml⁻¹). Discussion: We conclude that transient excessive decreasing G hypotension may occur during the decreasing G phase, which may be due to anti-G suit functioning.

Powell DMC, Spencer MB, Petrie KJ. Automated collection of fatigue ratings at the top of descent: a practical commercial airline tool. Aviat Space Environ Med 2011; 82:1037–41.Introduction: There is a need to develop an efficient and accurate way of assessing pilot fatigue in commercial airline operations. We investigated the validity of an automated system to collect pilot ratings of alertness at the top of descent, comparing the data obtained with existing results from previous studies and those predicted by the validated SAFE fatigue model. Methods: Boeing 777 pilots were prompted to enter a Samn-Perelli fatigue scale rating directly into the flight management system of the aircraft shortly prior to descent on a variety of short- and long-haul commercial flights. These data were examined to evaluate whether the patterns were in line with predicted effects of duty length, crew number, and circadian factors. We also compared the results with data from previous studies as well as SAFE model predictions for equivalent routes. Results: The effects of duty length, time of day, and crew complement were in line with expected trends and with data from previous studies; the correlation with predictions from the SAFE model was high (r = 0.88). Fatigue ratings were greater on longer trips (except where mitigated by adding an extra pilot) and on overnight sectors (4.68 vs 3.77). Discussion: The results suggest that the automated collection of subjective ratings is a valid way to collect data on fatigue in an airline setting. This method has potential benefits for the crew in assessing fatigue risk prior to approach, as part of a fatigue risk management system, with the possibility of wider safety benefits.

Kang S, Hwang S, Lee ET, Yang S, Park J. Measuring the cumulative effect of G force on aviator neck pain. Aviat Space Environ Med 2011; 82:1042–8.Introduction: In many studies, high G force is thought to be the most important causal factor of aviator neck pain. However, most of the studies performed to date have compared neck pain of aviators exposed to high G force with that of aviators not so exposed or with that of the general population. As a result, neck pain for aviators exposed to high G force as it relates to G level is not yet well-known. Methods: The subjects were 1003 male aviators who were sent an anonymous questionnaire. Subject variables were information on physical characteristics, lifestyle, and flight characteristics, including information about exposed maximum G (G_max). There were three dependent variables: whether the aviator had experienced neck pain, frequency of neck pain, and subjective severity of neck pain. Result: With the multivariate analysis, amount of G_max exposure (frequency or monthly duration of G_max exposure) had a statistically significant positive relationship with all three dependent variable. BMI, flight hours in current aircraft, and posterior seat type had a meaningful positive relationship with experience of neck pain and subjective severity of neck pain. Other characteristics, including G_max level, were not significantly related with any dependent variables. Discussion: These results suggest that G level could have a ceiling effect; in other words, above a certain G level, aviator neck pain risk does not increase. This means that amount of G_max exposure becomes more influential on aviator neck pain than the level of G_max.

Anderson JL, Waters MA, Hein MJ, Schubauer-Berigan MK, Pinkerton LE. Assessment of occupational cosmic radiation exposure of flight attendants using questionnaire data. Aviat Space Environ Med 2011; 82:1049–54.Introduction: Female flight attendants may have a higher risk of breast and other cancers than the general population because of routine exposure to cosmic radiation. As part of a forthcoming study of breast and other cancer incidence, occupational cosmic radiation exposure of a cohort of female flight attendants was estimated. Methods: Questionnaire data were collected from living female cohort members who were formerly employed as flight attendants with Pan American World Airways. These data included airline at which the flight attendant was employed, assigned domicile, start and end dates for employment at domicile, and number of block hours and commuter segments flown per month. Questionnaire respondents were assigned daily absorbed and effective doses using a time-weighted dose rate specific to the domicile and/or work history era combined with self-reported work history information. Results: Completed work history questionnaires were received from 5898 living cohort members. Mean employment time as a flight attendant was 7.4 yr at Pan Am and 12 yr in total. Estimated mean annual effective dose from all sources of occupational cosmic radiation exposure was 2.5 ± 1.0 mSv, with a mean career dose of 30 mSv. Discussion: Annual effective doses were similar to doses assessed for other flight attendant cohorts; however, questionnaire-based cumulative doses assessed in this study were on average higher than those assessed for other flight attendant cohorts using company-based records. The difference is attributed to the inclusion of dose from work at other airlines and commuter flights, which was made possible by using questionnaire data.

Nakagawara VB, Montgomery RW, Wood KJ. Laser illumination of flight crewmembers by altitude and chronology of occurrence. Aviat Space Environ Med 2011; 82:1055–60.Introduction: The illumination of flight crew personnel by lasers while they perform landing and departure maneuvers has concerned the aviation community for the past two decades. This study examines the frequency of illumination events in the United States by altitude and chronology of occurrence to determine where and when aviators and the flying public may be at greatest risk. Methods: Reports of aircraft illuminated by high-intensity light sources are maintained in a database at the Federal Aviation Administration's Civil Aerospace Medical Institute. Reports of flight crewmembers exposed to lasers from January 1, 2004, to December 31, 2008, were collected and analyzed. Results: Cockpit illuminations at or below 2000 ft (~610 m) increased from 12.5 to 26.7% over the 5-yr period, while the percentage of illuminations between 2000 and 10,000 ft (~610–3048 m) decreased from 87.5 to 58.4%. The months of November and December had the highest frequency of laser events (23%), while May and June had the least (12%). Sunday was the most likely day for an aircraft to be illuminated (18.3%), while Wednesday was the least likely day for such an incident (15.4%). More than 91% of all aircraft illumination events occurred between 1800 and midnight. Conclusion: The continuing increase in the number of laser illuminations reported at or below 2000 ft (~610 m) represents an escalating threat to aviation safety. Information provided in this study may allow law enforcement to deploy their resources more efficiently to apprehend those responsible for these crimes.

Rayman RB. Irritable bowel syndrome: aeromedical considerations. Aviat Space Environ Med 2011; 82:1061–3.Irritable bowel syndrome (IBS) is a gastrointestinal disorder diagnosed in accordance with the Rome III criteria. The pathophysiology of this illness is not well defined and there are no known structural abnormalities, biomedical markers, nor inflammatory causes to explain the symptoms. There are a number of serious illnesses, such as colon cancer, ulcerative colitis, and celiac disease that mimic IBS. If the Rome III criteria are satisfied and there are no alarm features of more serious illness, an in-depth workup is not necessary. There are numerous treatment regimens for IBS, none of which are curative nor offer universal relief. Some of the treatment regimens, such as antispasmodics and antidiarrheals, are not suitable for aviators because of anticholinergic effects and sedation. The aeromedical disposition decision is always challenging because of the vagaries of this illness. In general, a more liberal policy for pilots in civil aviation would be in order as long as symptoms are not frequent nor severe and not requiring antispasmodics or antidiarrheals while flying. A more conservative policy is in order for military pilots, possibly requiring restriction to multiseat aircraft.

Karydes HC, Zautcke JL, Zell-Kanter M. Chemical and traumatic occupational eye exposures in aviation personnel. Aviat Space Environ Med 2011; 82:1064–6.Introduction: The eye is vulnerable to chemical exposure and foreign body infiltration in the occupational setting. Individuals working in the aviation field are prone to these types of exposures. Methods: We conducted a 28-mo retrospective chart review to document the number of airline workers complaining of chemical or foreign body exposure to the eye at an onsite airport medical clinic. The International Classification of Diseases, Ninth Revision (ICD-9), code for chemical conjunctivitis (372.5), was used to identify patients’ charts. We documented the type of treatment that was initiated and whether there was eye damage. We further investigated the chemical composition of the products and whether there was any associated toxicity. Results: Few instances of chemical exposure and foreign body infiltration were found. Patients were exposed to the following products: lubricants (e.g., naphthenic oils), hydraulic fluid (e.g., petroleum or phosphate ester based), jet fuel (e.g., kerosene), and de-icing agents (e.g., propylene glycol). There was no documentation regarding the use of personal protection equipment in the patients’ charts. All patients received eye irrigation with normal saline. No sequelae were documented. Conclusion: Airline personnel are exposed to a variety of chemical agents in the workplace. None of the agents that workers were exposed to in this small study exhibited toxic effects to the eye. Proper use of personal protection equipment in aviation personnel may limit the number of chemical and foreign body eye exposures.

Rogers D, Boyd DD, Fox EE, Cooper S, Goldhagen M, Shen Y, del Junco DJ. Prostate cancer incidence in u.S. Air Force aviators compared with non-aviators. Aviat Space Environ Med 2011; 82:1067–70.Introduction: Several studies investigating whether prostate cancer incidence is elevated in aviators both in the civilian and military sectors have yielded inconsistent findings. Most investigations have compared aviators to the general population. Instead, our study compared prostate cancer incidence rates among officer aviators and non-aviators in the U.S. Air Force (USAF) to reduce confounding by socioeconomic status and frequency of medical exams. Methods: This retrospective analysis ascertained prostate cancer cases using the Automated Cancer Tumor Registry of the Department of Defense linked to personnel records from the USAF Personnel Center to identify aviators and non-aviators. Survival analysis using the Cox Proportional Hazards model allowed comparison of prostate cancer incidence rates in USAF aviators and non-aviators. Results: After adjustment for age and race, the hazards ratio for prostate cancer incidence comparing aviators with non-aviators was 1.15 (95% confidence interval, 0.85–1.44). Neither prostate cancer incidence nor time to diagnosis differed significantly between the two groups. Conclusion: Our study compared prostate cancer rates in aviators with a reference group of non-aviators similar in socio-economic level and frequency of exams. When compared to this internal reference group the risk of prostate cancer in USAF officer aviators appeared similar with no significant excess.

Grenon SM, Saary J. Challenges in aerospace medicine education. Aviat Space Environ Med 2011; 82:1071–2.Aerospace medicine training and research represents a dream for many and a challenge for most. In Canada, although some opportunities exist for the pursuit of education and research in the aerospace medicine field, they are limited despite the importance of this field for enabling safe human space exploration. In this commentary, we aim to identify some of the challenges facing individuals wishing to get involved in the field as well as the causal factors for these challenges. We also explore strategies to mitigate against these.

Doarn CR. Medical policy development for human spaceflight at NASA: an evolution. Aviat Space Environ Med 2011; 82:1073–7.Codification of medical policy for the National Aeronautics and Space Administration (NASA) did not occur until 1977. Policy development was based on NASA's human spaceflight efforts from 1958, and the need to support the operational aspects of the upcoming Space Shuttle Program as well as other future activities. In 1958, the Space Task Group (STG), a part of the National Advisory Committee on Aeronautics (NACA), became the focal point for astronaut selection, medical support, and instrumentation development in support of Project Mercury. NACA transitioned into NASA in 1958. The STG moved to Houston, TX, in 1961 and became the Manned Spacecraft Center. During these early years, medical support for astronaut selection and healthcare was provided through arrangements with the U.S. military, specifically the United States Air Force, which had the largest group of subject matter experts in aerospace medicine. Through most of the 1960s, the military worked very closely with NASA in developing the foundations of bioastronautics and space medicine. This work was complemented by select individuals from outside the government. From 1958 to 1977, there was no standard approach to medical policy formulation within NASA. During this time, it was individualized and subjected to political pressures. This manuscript documents the evolution of medical policy in the NASA, and provides a historical account of the individuals, processes, and needs to develop policy.

Hughes KG. You're the flight surgeon: aortic insufficiency. Aviat Space Environ Med 2011; 82:1082–3.