PURPOSE: To evaluate the use of the Cone Contrast Test (CCT) as a color vision screening tool in an Asian population of aircrew applicants and compare it against the Ishihara Psuedo Isochromatic Plates (PIP) – Edridge Lantern Test (ELT) screening pathway, assessing its impact on attrition with CCT cut-off scores of 55 and 75.METHODS: This is a retrospective review of 862 Republic of Singapore Airforce aircrew applicants tested with CCT and Ishihara PIP–ELT combination as screening. CCT repeatability was analyzed by comparing the subject’s interocular (right vs. left eye) scores measured as the coefficient of repeatability (COR), with COR differing by ≥15 points considered to be outside normal limits.RESULTS: Of the applicants, 17 (1.97%) failed to achieve a CCT score of ≥55 (5 protan, 12 deutan), while 26 (3.02%) applicants failed to achieve a score ≥75 (5 protan, 21 deutan). Of the 17 applicants who obtained a CCT score of <55, 16 failed the Ishihara PIP test. The only applicant who passed the Ishihara PIP test had a CCT score of 50. Of all applicants, 1.7% had a COR of ≥15, with 93.3% of them identified as color vision deficient (CVD). Our results demonstrated excellent test repeatability, with 99.9% (835 out of 836) of color vision normal (CVN) applicants achieving a COR of <15 points.CONCLUSION: Our study demonstrated a high correlation between the CCT (passing score of ≥55) and the Ishihara PIP. Employing the CCT with a passing score of ≥75, instead of the Ishihara PIP–ELT combination, led to an increase in attrition rate of 0.7–3.0%.Chay IW, Lim SWY, Tan BBC. Cone Contrast Test for color vision deficiency screening among a cohort of military aircrew applicants. Aerosp Med Hum Perform. 2019; 90(2):71–76.

BACKGROUND: The perception-action coupling task (PACT) was designed as a more ecologically valid measure of alertness/reaction times compared to currently used measures by aerospace researchers. The purpose of this study was to assess the reliability, within-subject variability, and systematic bias associated with the PACT.METHODS: There were 16 subjects (men/women = 9 / 7; age = 27.8 ± 3.6 yr) who completed 4 identical testing sessions. The PACT requires subjects to make judgements on whether a virtual ball could fit into an aperture. For each session, subjects completed nine cycles of the PACT, with each cycle lasting 5 min. Judgement accuracy and reaction time parameters were calculated for each cycle. Systematic bias was assessed with repeated-measures ANOVA, reliability with intraclass correlation coefficients (ICC), and within-subject variability with coefficients of variation (CV_TE).RESULTS: Initiation time (Mean = 0.1065 s) showed the largest systematic bias, requiring the elimination of three cycles to reduce bias, with all other variables requiring, at the most, one. All variables showed acceptable reliability (ICC > 0.70) and within-subject variability (CV_TE < 20%) with only one cycle after elimination of the first three cycles.CONCLUSIONS: With a three-cycle familiarization period, the PACT was found to be reliable and stable.Connaboy C, Johnson CD, LaGoy AD, Pepping G-J, Simpson RJ, Deng Z, Ma L, Bower JL, Eagle SR, Flanagan SD, Alfano CA. Intersession reliability and within-session stability of a novel perception-action coupling task. Aerosp Med Hum Perform. 2019; 90(2):77–83.

INTRODUCTION: Carbon monoxide (CO) is a toxic gas with potential for detriment to spaceflight operations. An analytical model was developed to investigate if a maximum CO contamination of 1 ppm in the oxygen (O₂) supply reached dangerous levels during extravehicular activity (EVA). Occupational monitoring pre- and postsuited exposures provided supplementary data for review.METHODS: The analytical model estimated O₂ and CO concentrations in the extravehicular mobility unit (EMU) based on O₂ and CO flow rates into and out of the system. The model was based on 3 h of prebreathe at 15.2 psia, 8 h of EVA at 4.3 psia, and 1 h at 15.2 psia for suit doffing. The Coburn-Forster-Kane equation was used to calculate crewmember carboxyhemoglobin saturation (COHb%) as a function of time. Monitoring of hemoglobin CO saturation (S_pco) with a CO-oximeter was conducted pre- and post-EVA during operations on the International Space Station and in ground-based analog environments.RESULTS: The model predicted a maximum P_CO in the EMU of 0.061 mmHg and a maximum crewmember COHb% of 2.1%. Operational S_pco measurements in mean ± SD during ground-based analog testing were 0.7% ± 1.8% pretest and 0.5% ± 1.5% posttest. S_pco values on the ISS were 1.5% ± 0.7% pre-EVA and 1.1% ± 0.3% post-EVA.DISCUSSION: The model predicted that astronauts are not exposed to toxic levels of CO during EVA and operational measurements did not show significant differences between S_pco levels between pre- and post-EVA.Makowski MS, Norcross JR, Alexander D, Sanders RW, Conkin J, Young M. Carbon monoxide levels in the extravehicular mobility unit by modeling and operational testing. Aerosp Med Hum Perform. 2019; 90(2):84–91.

INTRODUCTION: Recently, portable dry electroencephalographs (dry-EEGs) have indexed cognitive workload, fatigue, and drowsiness in operational environments. Using this technology this project assessed whether significant changes in brainwave frequency power occurred in response to hypoxic exposures as experienced in military aviation.METHODS: There were 60 (30 women, 30 men) student Naval Aviators or Flight Officers who were exposed to an intense (acute) high-altitude (25,000 ft) normobaric hypoxic exposure, and 20 min later, more gradual (insidious) normobaric hypoxic exposure up to 20,000 ft while flying a fixed-wing flight simulation and monitored with a dry-EEG system. Using MATLAB, EEG frequencies and power were quantified and analyzed. Cognitive performance was also assessed with a cognitive task validated under hypoxia. Normobaric hypoxia and O₂ saturation (Spo₂) were produced and monitored using the Reduced Oxygen Breathing Device (ROBD2).RESULTS: Significant Spo₂ decreases were recorded at acute 25K and insidious 20K simulated altitudes. Significant power decreases were recorded in all frequencies (alpha, beta, gamma, and theta) and all channels with acute 25K exposures. Gamma, beta, and theta frequency power were significantly decreased with insidious 20K exposures at most of the channels. The frequency power decreases corresponded to significant decreases in cognitive performance and flight performance. Most importantly, frequency power suppressions occurred despite 42% of the volunteers not perceiving they were hypoxic in the acute phase, nor 20% in the insidious phase.DISCUSSION: Results suggest EEG suppression during acute/insidious hypoxia can index performance decrements. These findings have promising implications in the development of biosensors that mitigate potential in-flight hypoxic physiological episodes.Rice GM, Snider D, Drollinger S, Greil C, Bogni F, Phillips J, Raj A, Marco K, Linnville S. Dry-EEG manifestations of acute and insidious hypoxia during simulated flight. Aerosp Med Hum Perform. 2019; 90(2):92–100.

BACKGROUND: Flight cadets’ emotion is a factor of great importance to flight training. So it is of profound significance to address how emotional factors affect flight training performance. The present study aimed to investigate the relationship between emotional intelligence (EI) and simulated flight performance (SFP), and explore the mechanism of emotional state as a mediator in the effect of EI on SFP.METHODS: Ninety undergraduates took part in the study. EI (Wong and Law Emotional Intelligence Scale), neuroticism (Eysenck Personality Questionnaire Revised), anxiety (State Anxiety Inventory), and tension (Profile of Mood States) were collected. Conducted were 9 h of simulated flight training in a simulator of the Type 6 Primary Trainer. The Delphi Experts Grading Method was used to assess students’ SFP. Mediation effect of emotional state was explored using regression analysis.RESULTS: EI was significantly correlated with neuroticism (r = −0.31), tension (r = −0.31), and anxiety (r = −0.31), respectively. Multiple mediation effects showed that emotional state mediated the association between EI and SFP. Tension especially mediated the associations between the Self Emotion Appraisals and Regulation of Emotion dimensions of EI and SFP. However, the Use of Emotion dimension of EI had a direct negative effect on SFP without the mediating role of emotional state.DISCUSSION: The findings indicated that EI was significantly correlated with emotional state (neuroticism, tension, and anxiety). EI may directly or indirectly affect SFP and tension played an important mediating role. Implications for the promotion of EI and emotional state to enhance performance in real flight training are discussed.Dai J, Wang H, Yang L, Wen Z. Emotional intelligence and emotional state effects on simulated flight performance. Aerosp Med Hum Perform. 2019; 90(2):101–108.

INTRODUCTION: Despite the clear need for understanding how pilot sleep affects performance during long-range (LR; 12-16h) and ultra-long-range (ULR; 16+h) flights, the scientific literature on the effects of sleep loss and circadian desynchronization on pilots’ sleep in commercial aviation is sparse.METHODS: We assessed pilots’ sleep timing, duration, and post-trip recovery on two LR and two ULR nonstop California to Australasia routes. Pilot’s sleep/wake history was measured with actigraphy and verified by logbook across 8–9 d.RESULTS: Pilots averaged 8.210 ± 1.687 SD hours of sleep per 24 h across the study period. A logistic model of the circadian timing of sleep indicated that time of day and phase of trip are significant predictors of pilots being asleep. Significant two- and three-way interactions were found between time of day, phase of trip, and route. A significant difference in average sleep time was observed between baseline and recovery day 1 for one route. All other recovery days and routes were not significantly different from baseline.DISCUSSION: For the four routes, the average amount of sleep per 24-h period during the study period was within the normal range with the circadian rhythm aligned to home-base time pre- and post-trip. Flight segments and layover conditions were associated with a misalignment of sleep relative to circadian rhythm, with layover sleep appearing to shift toward the local night. Full post-trip sleep duration recovery appears to occur for all routes within 1–2 d.Lamp A, McCullough D, Chen JMC, Brown RE, Belenky G. Pilot sleep in long-range and ultra-long-range commercial flights. Aerosp Med Hum Perform. 2019; 90(2):109–115.

BACKGROUND: Space is a special environment in which microgravity and cosmic rays are the primary factors that induce gene mutations of microorganisms. In our previous studies, a single point mutation in the gene dprA was found in an Enterococcus faecium strain of LCT-EF258 after spaceflight. DNA processing protein A (DprA) plays a prominent role in the horizontal transfer of genes among bacteria (such as Streptococcus pneumoniae, Helicobacter pylori, Bacillus subtilis, and Rhodobacter capsulatus). However, the function of DprA in E. faecium remains unknown. Furthermore, E. faecium could acquire antibiotic resistance through the horizontal transfer of antibiotic resistance genes, but it is unclear whether dprA mutants could affect this process in E. faecium.METHODS: In this study, we constructed a plasmid containing the vancomycin resistance gene vanA and then transferred the gene vanA into the dprA-mutant strain LCT-EF258 and the control strain LCT-EF90 using the electroporation technique. We then used Discovery Studio^TM software to construct the 3D protein structure.RESULTS: The results showed that the horizontal transfer efficiency of the vancomycin resistance gene vanA in the dprA-mutant E. faecium decreased. And the hydrophobic core of the mutant DprA became stable and the binding affinity between the mutant DprA and ssDNA reduced.DISCUSSION: This study is an exploration of bacterial gene mutation after spaceflight. The dprA mutant could affect the ability of E. faecium to acquire exogenous resistance gene vanA, which offered us an interesting path to block the dissemination of resistance genes between strains.Yu Y, Chang D, Guo Q, Wang J, Liu C. LCT-EF258 with S171 mutation in DprA exhibits horizontal gene transfer deficiency after spaceflight. Aerosp Med Hum Perform. 2019; 90(2):116–122.

BACKGROUND: The incidence of hot-air balloon tour accidents in Turkey is not clear, as published data are scarce. This study aimed to determine the rate of such accidents, including passenger fatalities and injuries, across all flight hours and to also compare these types of accidents to those of other commercial air tour crashes.METHODS: Hot-air balloon tour accident reports in the Cappadocia region were analyzed for 1,415,943 passengers during 81,112 flight hours undertaken between August 2013 and July 2017. The flight and accident data were obtained from the Accident Investigation Board and the Directorate General of Civil Aviation.RESULTS: There were 12 accidents which occurred during the flight hours examined (a rate of 14.8 accidents per 100,000 h). There were 33 individuals seriously injured, 3 fatally in all passengers (3.7 fatalities per 100,000 h in these flights). The majority of accidents that produced serious and fatal injuries occurred during the last year of the study. The most common cause of accidents was a hard landing (58.3%). All accidents occurred during the landing phase of the flight. Seven patients experienced multiple traumas and lower extremity injuries constituted the majority of cases (N = 21).DISCUSSION: The fatality rate of commercial balloon rides was lower than that for lighter-than-air craft, which include balloons and blimps (sports aviation flights), and the crash rate of hot-air balloons was higher than those of aircraft (airplanes and helicopters) tour flights. However, there is still insufficient information in the literature to properly compare this activity with commercial motorized aircraft tours and other hot-air balloon flights.Aslaner MA. Hot-air balloon tour accidents in the Cappadocia region. Aerosp Med Hum Perform. 2019; 90(2):123–127.

BACKGROUND: Barodontalgia, barometric pressure-induced dental pain, may jeopardize diving/flight safety. The aim of this systematic review was to investigate the rate of barodontalgia among military and civilian divers and aircrews based on previous reports.METHODS: We analyzed the data of 4894 aircrew/divers reported in the literature. Barodontalgia rates (flight vs. diving, military vs. civilian, pressurized vs. non-pressurized aircrafts) were analyzed. The Chi-squared test was used to compare between groups.RESULTS: Of the 4894 individuals, 402 (8.2%) suffered from barodontalgia. Divers (9.8%) were more vulnerable than aircrews (5.8%). Barodontalgia experience rate was 5.4% and 6.5% in military and civilian aircrews, respectively, and 7.3% and 12.8% in military and civilian scuba divers, respectively. Barodontalgia was more common among aircrews of pressurized than non-pressurized aircrafts (7.3% vs. 3.2%, respectively).DISCUSSION: The greater amplitude of barometric pressure changes explains the higher rate of barodontalgia in divers than aircrew. The higher rate during pressurized flights is possibly because intracabin pressure in the pressurized cabin is still routinely higher than in nonpressurized aircrafts. Improved oral care and mandatory annual dental checkups may be the reason for the significantly lower rate of barodontalgia experienced among military aircrews and divers compared to their civilian counterparts. These results emphasize the essential role of atmospheric pressure change in the generation of pain during flight or diving and the importance of proper dental care.Nakdimon I, Zadik Y. Barodontalgia among aircrew and divers. Aerosp Med Hum Perform. 2019; 90(2):128–131.

BACKGROUND: Internal jugular phlebectasia (IJP) is an uncommon entity with only about 100 reported cases and with very few available cases in the literature. The current case study is about a male trainee fighter pilot incidentally diagnosed to have IJP. With limited literary evidence, it was a complex task to predict the prognosis of IJP and its implications on fighter flying.CASE REPORT: In order to confirm the diagnosis, a preliminary study was carried out to find out the normal and expanded area of the internal jugular vein (IJV) of 30 volunteers. The expanded area of the right IJV of the trainee pilot fell beyond 1 SD of the study population, confirming the diagnosis of IJP in the trainee pilot.DISCUSSION: Aeromedical concerns were the anti-G straining maneuver, positive pressure breathing for G, negative G_z, modified Valsalva maneuver, and rapid decompression. Considering the potential progression of IJP by repeated exposure to aviation stresses, the trainee pilot was re-assigned to helicopters.Khatua SS, Sannigrahi P, Dahiya M, Rastogi P, Raheem A. Aeromedical decision making in internal jugular phlebectasia. Aerosp Med Hum Perform. 2019; 90(2):132–134.

INTRODUCTION: In February 1970, halfway through a Polaris submarine war patrol in SSBN-02 HMS Renown (port crew), a Petty Officer presented to the sick bay in excruciating pain with a broken upper left molar tooth. The zinc oxide/clove oil mixture would not stick on to the vertical face of the fracture. In preparation for such events, Royal Navy (RN) submarine medical officers are taught excellent fundamental dental skills. In this case, it seemed a very difficult job to extract the remains of the tooth. The author reports the first known use of glass fiber/resin in the RN to crown and treat a fractured molar, cover the root, and save the tooth, and to recommend that all military and civilian medical staff working anywhere in isolation with no dental facility locally be given similar training to that which RN submarine medical officers receive before being sent on extended dives.Brooks CJ. Fractured tooth stabilized with auto body repair resin on a 1970 Royal Navy Polaris submarine patrol. Aerosp Med Hum Perform. 2019; 90(2):135–138.

Nolan CF. You’re the flight surgeon: scarlet fever. Aerosp Med Hum Perform. 2019; 90(2):139–143.