BACKGROUND: Although the understanding of hypobaric hypoxia is increasing, it remains a hazard in aviation medicine. This study examined the feasibility of detecting voice markers sensitive to acute hypobaric hypoxia in an early presymptomatic (PRE-SYMP) stage.METHOD: Eight subjects qualified with hypobaric training completed a series of standardized speech tests in a hypobaric chamber at 20,000 ft and 25,000 ft (6096 and 7620 m) of altitude. Voice response patterns were analyzed in terms of fundamental frequency (F0), F0 range, and voice onset time (VOT). We hypothesized a PRE-SYMP compensatory stage in voice reactivity.RESULTS: There was a different dose-response reactivity course at 20,000 ft vs. 25,000 ft, nonlinear to altitude. At 20,000 ft, our hypothesis was confirmed. In comparison to sea level, a PRE-SYMP compensatory stage could be distinguished, characterized by a decreased F0 range, decreased VOT, and increased F0. During a transitional (TRANS) stage, in comparison with sea level, the F0-range reset, VOT decreased, and F0 increased. During a symptomatic (SYMP) stage, F0 increased, F0 range increased, and VOT decreased. At 25,000 ft, in comparison to sea level, voice reactivity showed increased F0 and F0 range and decreased VOT in a PRE-SYMP stage and increased F0 and F0 range in the SYMP stage.DISCUSSION: The compensatory PRE-SYMP stage is suggested to be the expression of ongoing bottom-up and top-down regulatory mechanisms, whereas the 25,000-ft results are interpreted as a combination of tonic and phasic voice reactivity. This tonic component needs to be foreseen in sea level baseline measures.Van Puyvelde M, Neyt X, Vanderlinden W, Van den Bossche M, Bucovaz T, De Winne T, Pattyn N. Voice reactivity as a response to acute hypobaric hypoxia at high altitude. Aerosp Med Hum Perform. 2020; 91(6):471–478.

INTRODUCTION: Being able to identify individual differences in skilled motor learning during disorienting conditions is important for spaceflight, military aviation, and rehabilitation.METHODS: Blindfolded subjects (N = 34) were strapped into a device that behaved like an inverted pendulum in the horizontal roll plane and were instructed to use a joystick to stabilize themselves across two experimental sessions on consecutive days. Subjects could not use gravitational cues to determine their angular position and many soon became spatially disoriented.RESULTS: Most demonstrated minimal learning, poor performance, and a characteristic pattern of positional drifting during horizontal roll plane balancing. To understand the wide range of individual differences observed, we used a Bayesian Gaussian Mixture method to cluster subjects into three statistically distinct groups that represent Proficient, Somewhat Proficient, and Not Proficient performance. We found that subjects in the Not Proficient group exhibited a suboptimal strategy of using very stereotyped large magnitude joystick deflections. We also used a Gaussian Naive Bayes method to create predictive classifiers. As early as the second block of experimentation (out of ten), we could predict a subject’s final group with 80% accuracy.DISCUSSION: Our findings indicate that machine learning can help predict individual performance and learning in a disorienting dynamic stabilization task and identify suboptimal strategies in Not Proficient subjects, which could lead to personalized and more effective training programs.Vimal VP, Zheng H, Hong P, Fakharzadeh LN, Lackner JR, DiZio P. Characterizing individual differences in a dynamic stabilization task using machine learning. Aerosp Med Hum Perform. 2020; 91(6):479–488.

INTRODUCTION: This study is conducted to observe the effects of cognitive load on the visual search and attention allocation strategies of pilots. Research on pilots’ visual search strategies can provide valuable information regarding attention distribution and transformation, as well as useful situation awareness (SA) predictions.METHODS: A total of 18 pilots performed flight tasks in a two-condition (high and low cognitive load) within-subject experiment to compare their flight performance and eye movement indicators. Eye movements were tracked during the flight mission by a portable eye-tracking device.RESULTS: Compared to the low cognitive load task, in the high cognitive load task, the subjects exhibited shorter average fixation times (M = 420.38, SD = 60.56), higher fixation frequencies (M = 2.27, SD = 0.30), and lower saccade frequencies (M = 2.7, SD = 0.31). Their flight performance was better during the low cognitive load task, as evidenced by the lower entropy (M = 0.11, SD = 0.03) of their eye movements. Analysis of fixation time percentages and fixation counts showed that the distribution of attention to each area of interest was adjusted dynamically over the course of the given task.DISCUSSION: Significant differences were observed in both fixation order and fixation frequency across the instrument array. When the cognitive load is high, the subjects used more efficient eye movement patterns and search strategies accompanying a higher level of SA.Lu T, Lou Z, Shao F, Li Y, You X. Attention and entropy in simulated flight with varying cognitive loads. Aerosp Med Hum Perform. 2020; 91(6):489–495.

BACKGROUND: Helicopter hoist operators are highly skilled and critical crewmembers in search and rescue. However, hoist operator training programs are relatively underdeveloped in comparison to helicopter pilot training. It is critical that this simulator teaches the necessary skills for high-level performance given the dangers associated with helicopter hoist operation. As a result, we sought to validate and identify critical aspects of skilled hoisting.METHODS: Through expert consultation, we identified several measures of hoist operation, such as mission time, cable plumb, cable tension, cable hand position, and cable displacement. We compared hoist performance between experienced and novice hoist operators in a simulated hoisting mission with two levels of difficulty (with and without wind). The experienced group (eight men/one woman) was composed of nine active or former military hoist operators who were working in commercial search and rescue. The novice group was composed of seven subjects (two men/five women) from the general population and had no previous experience with hoisting operations or the simulator.RESULTS: We found that experienced hoist operators had faster mission time, similar cable plumb, lower tension, and less variable hand position. Further, experienced hoist operators pulled the cable inward in the wind while novice hoist operators pushed the cable away.DISCUSSION: These findings suggests that this simulator captures performance differences between skill levels and, as a result, is a first step supporting the use of this simulator for hoist operator training.King MT, Lenser S, Rogers D, Carnahan H. Helicopter hoist performance in novice and experienced hoist operators. Aerosp Med Hum Perform. 2020; 91(6):496–500.

INTRODUCTION: Understanding UV exposure is essential for the assessment of its contribution to the occupational risk of pilots developing ocular and skin pathologies. The objective of this observational study was to measure the UV exposure of pilots flying between the United Kingdom and a range of destinations at three different seasons.METHODS: The in-flight UV exposure of pilots was measured on 322 Monarch Airlines short-haul flights on the Airbus A321-231 and Airbus A320-214 to 31 destinations, mostly in Europe, from 4 UK airports in September 2016–August 2017. The erythema effective and UV-A doses were compared with the ICNIRP guidance and typical recreational weekend exposure of UK office workers.RESULTS: The erythema effective radiant doses did not exceed 0.1 SED. For most of the flights, the UV-A exposure was also low. On 27 single sector flights, UV-A exposure could have exceeded the ICNIRP guidance if eye protection was not used.DISCUSSION: The UV exposure in a cockpit is mostly governed by the presence of direct sunlight and the duration of a flight. The average monthly exposures were low and significantly below weekend recreational exposures of UK office workers over a similar period. To assess the contribution of occupational UV exposure to the risk of developing sun-related ocular and cutaneous pathologies, it is important to consider the accumulative flight time, destinations, and UV attenuation of aircraft windshields. Additionally, leisure and recreational outdoor time needs to be considered before meaningful overall risk analysis can be undertaken.Baczynska KA, Brown S, Chorley AC, O’Hagan JB, Khazova M, Lyachev A, Wittlich M. In-flight UV-A exposure of commercial airline pilots. Aerosp Med Hum Perform. 2020; 91(6):501–510.

BACKGROUND: Since eye movement can provide a reliable index of the attention allocation, which can assist in understanding pilots’ cognitive state, this study investigated the effect of pilots’ experience and the autopilot mode on their attention allocation on the Primary Flight Display (PFD) and Multi-Function Display (MFD) during an approach task.METHODS: There were 16 pilots who were classified into two levels of aviation expertise depending on the flight hours, and required to fly an Instrument Landing System approach. Their visual scanning behaviors were recorded through an eye tracker and analyzed based on fixation number and dwell time.RESULTS: The results revealed that the pilot experience level, instrument panel and autopilot mode all had significant impact on the fixation time ratio and dwell time. The pilots fixated most often on the PFD and had shorter dwell time. Furthermore, they had a lower fixation number and shorter dwell time on the PFD and MFD when the autopilot was off that they should allocate visual resources to the others (e.g., out-of-the-window) and obtain more information to maintain overall situation awareness under higher time pressure. Compared to pilots with more expertise, pilots with less expertise had an increased fixation number and decreased dwell time on the airspeed after turning off the autopilot.DISCUSSION: The present study indicated that the pilots had different visual scanning modes according to the flight mode and their experience. We expect that pilots’ visual scanning behaviors during tasks will help the training and the design of the human-machine interaction.Lu Y, Zheng Y, Wang Z, Fu S. Pilots’ visual scanning behaviors during an instrument landing system approach. Aerosp Med Hum Perform. 2020; 91(6):511–517.

BACKGROUND: Fatigue is a well-known hazard in aviation. In military fighter communities, policies have evolved to allow for in-flight use of pharmacological vigilance aids to counteract the negative effects of fatigue. With limited objective evidence supporting the role of these medications in continuous flight operations, the present study seeks to evaluate whether use of modafinil is associated with pilot aircraft carrier landing performance.METHODS: A retrospective, observational study was completed following carrier-based flight operations in support of Operation Inherent Resolve. All graded landing passes were included in the analysis. Mixed-effect multivariate linear regression analysis was utilized for the primary outcome of landing signal officer grade of landing performance following combat sorties for events with reported in-flight use of modafinil.RESULTS: A total of 1122 sorties were flown by 79 different pilots with an average landing pass grade of 3.86. The primary outcome of modafinil use in-flight was not generally associated with landing performance. In a subset analysis of more senior ranked aviators, modafinil use appeared to offer a relative performance improvement back to baseline (+0.19). Secondary outcome analysis revealed landing performance was associated with advanced landing technologies (+0.25), sorties later in deployment (+0.05 per 30 d), total career carrier landings (+0.03 per 100 traps), and longer mission duration (-0.04 per hour).DISCUSSION: In the context of evidence supporting subjective benefits of vigilance aid use by aircrew, the results of this study provide ample objective support to the controlled use of modafinil in the operational environment.Schallhorn CS. Vigilance aid use and aircraft carrier landing performance in pilots of tactical aircraft. Aerosp Med Hum Perform. 2020; 91(6):518–524.

INTRODUCTION: Aerospace orthostatic intolerance garments (OIG) have historically been pneumatic (e.g., NASA’s antigravity suit), an approach that inhibits mobility and requires connection to an air supply. Elastic compression garments, an alternative technology, are difficult to don/doff and cannot be worn in a noncompressive state, resulting in discomfort and usability challenges. This research evaluates a novel technology—contractile shape memory alloy (SMA) knitted actuators—that can enable low-profile, dynamic compression for an aerospace OIG.METHODS: To characterize the functional capabilities of SMA knitted actuators, displacement control testing was conducted on 10 actuator samples with a range of geometric design parameters. Inactive (F_I) and actuated forces (F_A) were observed by repeatedly thermally cycling each sample at 0%, 15%, 30%, and 45% structural strain. Compression capabilities were approximated using medical compression hosiery standards and anthropometric data from a representative aerospace population (ANSUR 2012).RESULTS: Dynamic compression predictions reached 52 mmHg (single layer fabric) and 105 mmHg (double layer fabric) at the ankle. Low, inactive pressures (p < 20 mmHg) demonstrate that compression is controllable and can be dynamically increased upon actuation up to 33 mmHg in a single layer system and up to 67 mmHg in a double layer system.DISCUSSION: The results highlight the potential of SMA knitted actuators to enable low-profile, dynamic compression garments that can reach medically therapeutic pressures on an aerospace population to counteract OI symptoms. In addition to astronautic applications, this technology demonstrates widespread terrestrial medical and high-performance aircraft applicability.Granberry RM, Eschen KP, Ross AJ, Abel JM, Holschuh BT. Dynamic countermeasure fabrics for post-spaceflight orthostatic intolerance. Aerosp Med Hum Perform. 2020; 91(6):525–531.

INTRODUCTION: In recent decades, there has been investigation into the effects of microgravity and microgravity-like environments on cognition and emotion separately. Here we highlight the need of focusing on emotion-cognition interactions as a framework for explaining cognitive performance in space. In particular, by referring to the affective cognition hypothesis, the significant interplay between emotional variables and cognitive processing in space is briefly analyzed. Altogether, this approach shows an interesting pattern of data pointing to a dynamic relation that may be sensitive to microgravity. The importance of examining interactions between emotion and cognition for space performance remains fundamental (e.g., stress-related disorders) and deserves further attention. This approach is ultimately interesting considering the potential effects that microgravity may play on human performance during long-term space missions and on return to Earth.Mammarella N. Towards the affective cognition approach to human performance in space. Aerosp Med Hum Perform. 2020; 91(6):532–534.