BACKGROUND: Short-term fluid loading is used as part of post-spaceflight medical procedures and clinical treatment in hospitals. Hypervolemia with hemodilution induced by rapid fluid infusion reportedly impaired dynamic cerebral autoregulation. However, the effects on intracranial pressure (ICP) remain unknown. Therefore, we estimated ICP noninvasively (nICP) to examine whether rapid fluid infusion would raise ICP.METHODS: Twelve healthy male volunteers underwent two discrete normal saline (NS) infusions (15 and 30 ml · kg⁻¹ stages, NS-15 and NS-30, respectively) at a rate of 100 ml · min⁻¹. The cerebral blood flow (CBF) velocity (CBFv) waveform from the middle cerebral artery obtained by transcranial Doppler ultrasonography was recorded, as was the arterial blood pressure (ABP) waveform at the radial artery obtained by tonometry. We then used these waveforms to calculate nICP, cerebral artery compliance, and the pulsatility index (PI) in an intracranial hydraulic model.RESULTS: nICP increased significantly in both infusion stages from preinfusion (preinfusion: 7.6 ± 3.4 mmHg; NS-15: 10.9 ± 3.3 mmHg; NS-30: 11.7 ± 4.2 mmHg). No significant changes were observed in cerebral artery compliance or PI. Although ABP did not change in any stage, CBFv increased significantly (preinfusion: 67 ± 10 cm · s⁻¹; NS-15: 72 ± 12 cm · s⁻¹; NS-30: 73 ± 12 cm · s⁻¹).DISCUSSION: Hypervolemia with hemodilution induced by rapid fluid infusion caused increases in nICP and CBFv. No changes were observed in cerebral artery compliance or PI related to cerebrovascular impedance. These findings suggest that rapid fluid infusion may raise ICP with increased CBF.Kurazumi T, Ogawa Y, Takko C, Kato T, Konishi T, Iwasaki K. Short-term volume loading effects on estimated intracranial pressure in human volunteers. Aerosp Med Hum Perform. 2022; 93(4):347–353.

INTRODUCTION: Pilot fatigue is a significant concern in aviation, where efforts are directed at improving rosters, developing models, and improving countermeasures. Little attention has been given to in-flight detection of fatigue/drowsiness. The aims of this research were to determine whether drowsiness is an issue and explore whether infrared reflectance oculography could prove useful for continuous inflight monitoring.METHODS: Nine university-based pilot trainees wore activity monitors and completed diaries, prior to a simulated navigational exercise of approximately 4 h, during the secondary window of circadian low. During the flight they wore a head-mounted device. Oculographic data were collected and converted into a single number, using the Johns Drowsiness Scale (JDS), with increasing values indicating greater drowsiness (range 0.0 to 10.0).RESULTS: Peak JDS values reached 6.5. Values declined from shortly before top of descent, continuing until landing. Two of the nine participants (22.2%), reached drowsiness levels at or above a cautionary warning level, below which is considered safe for driving a motor vehicle.DISCUSSION: The results of this study revealed the timeline and levels of fatigue that might be experienced by student pilots; showing that drowsiness is a potential issue for student pilots operating in flying conditions similar to those in the simulation. Analysis indicated that pilots are likely to experience levels of drowsiness above a cautionary warning level when modeling predicted effectiveness below 90%, indicating a potential drowsiness issue for pilots. It was concluded that oculography is worthy of further investigation for use as an objective fatigue detection tool in aviation.Corbett MA, Newman DG. Student drowsiness during simulated solo flight. Aerosp Med Hum Perform. 2022; 93(4):354–361.

OBJECTIVES: This study investigated the effectiveness and identified the cutoff values of the computer-based Farnsworth-Munsell 100-Hue (CFM-100) test for screening color vision deficiencies in the pre-employment examination of civil aviators in China.METHODS: Firstly, subjects were stratified into normal, color weakness, and color blindness with the Ishihara pseudoisochromatic plate test (IPPT) by two ophthalmologists. Then they randomly completed CFM-100 and Farnsworth-Munsell 100-Hue (FM-100) tests. Total error scores (TES) and the time taken for the CFM-100 and FM-100 were analyzed and the cutoff values for the CFM-100 were determined.RESULTS: Of 218 subjects, 159 were normal while 59 were diagnosed with dyschromatopsia. The TES of the CFM-100 were congruent with those of the FM-100 (20.0 ± 18.8 vs. 20.6 ± 17.7, 160.9 ± 66.0 vs. 151.1 ± 66.4). The testing time for the CFM-100, however, was less than the FM-100 (10.3 ± 2.8 min vs. 12.9 ± 2.9 min, 7.8 ± 2.5 min vs. 12.6 ± 3.3 min). The correlation coefficient R was 0.93 and Cohen’s kappa was 0.89 for the two methods. Further analyses defined 34 as the cutoff value to differentiate excellent from fair color discrimination (sensitivity 58.0%, specificity 94.7%) and 101 as the cutoff value to judge fair vs. poor (sensitivity and specificity both 98.8%) for the CFM-100. The cut-off value was 72 for distinguishing normal from defective color vision (sensitivity 96.6%, specificity 98.7%) and 110 was for distinguishing color weakness from color blindness (sensitivity 97.6%, specificity 97.7%) for the CFM-100.CONCLUSIONS: The CFM-100 is an effective method for the diagnosis of dyschromatopsia with high sensitivity in screening airline pilots.Zhang Y, Ma J, Cheng S, Hu W. A computer-based Farnsworth-Munsell 100-Hue (CFM-100) test in pilots’ medical assessments. Aerosp Med Hum Perform. 2022; 93(4):362–367.

INTRODUCTION: In commercial aviation, pilot fatigue is a major threat to safety. One key fatigue mitigation strategy on long-range (LR; 8–16 h) and ultra-long range (ULR; 16+ h on at least 10% of trips) routes is allotting in-flight rest breaks for the pilots. Since sleep is a strong predictor of performance, it is important to quantify total in-flight sleep (TIFS) and determine rest scheme schedules that optimize sleep opportunity and subsequent performance. Here we quantify in-flight sleep and characterize rest schemes by type and efficiency.METHODS: Between 2015 and 2019, we collected data on in-flight sleep on 3 LR and 5 ULR routes totaling 231 pilots flying over 1200 flight duty periods. Data were collected using a combination of actigraphy and logbooks.RESULTS: Over all combinations of flight direction, crew and LR vs. ULR, average TIFS ranged from 3.4 h to 5.2 h with some ULR pilots getting over 8 h. Most crews made use of simple two- or three-break rest schemes and the complex four-break rest schemes were used almost exclusively on the three longest ULR routes. The complex schemes were less efficient than simple schemes, although this effect was small. Complex schemes resulted in no more TIFS compared to simple schemes on the same routes.DISCUSSION: Overall, we find that crews are getting more sleep on these routes than previously reported on similar routes. Most crews use simple rest schemes and these simple schemes are more efficient than complex schemes.Rempe MJ, Basiarz E, Rasmussen I, Belenky G, Lamp A. Pilot in-flight sleep during long-range and ultra-long range commercial airline flights. Aerosp Med Hum Perform. 2022; 93(4):368–375.

BACKGROUND: The applicants’ self-declaration of medical history is crucial for safety. Some evidence indicates that under-reporting of medical conditions exists. However, the magnitude in a population of aviation personnel has not been reported earlier.METHODS: A total of 9941 applicants for medical certificate/attestation for aviation-related safety functions during the last 5 yr up to December 2019 were registered at the Civil Aviation Authority Norway. E-mail addresses were known for 9027 of these applicants, who were invited to participate in a web-based survey.RESULTS: Among the 1616 respondents, 726 (45%) were commercial pilots, 457 (28%) private pilots, 272 (17%) air traffic controllers, and the remaining were cabin crew or crew in aerodrome/helicopter flight information service (AFIS or HFIS, respectively). A total of 108 were initial applicants. The age group 50+ constituted the largest proportion of respondents (53%). Aeromedical certification in general was believed to improve flight safety “to a high” or “very high extent” by 64% of the respondents. A total of 188 individuals (12%) admitted having under-reported information related to one or more categories, including mental (3%) or physical health (4%), medications (2%), and drug use, including alcohol use (5%). Among these, 21 participants believed their own under-reporting “to some” or “to a high extent” affected flight safety. In total 50% of noninitial applicants reported that they knew colleagues who had under-reported information. Analyses revealed that being a commercial pilot showed a higher risk for under-reporting compared with other classes and the perception of aeromedical examiners in a supportive or authoritative role reduced the risk.CONCLUSIONS: Under-reporting of medical conditions could be significant in aviation. Further studies should be conducted to investigate the true extent of under-reporting and its impact on flight safety and what mitigating measures might be recommended.Strand T-E, Lystrup N, Martinussen M. Under-reporting of self-reported medical conditions in aviation: a cross-sectional survey. Aerosp Med Hum Perform. 2022; 93(4):376–383.

BACKGROUND: Medical selection criteria for Israeli Air Force (IAF) Flight Academy candidates are strict due to the extreme physiological stressors during military flight. In various air forces the causes for medical disqualification of Flight Academy candidates are different, mainly due to differences in the selection process and criteria. In the present study, we examined the medical conditions leading to disqualification of candidates for the IAF Flight Academy.METHODS: We reviewed the medical records of 3281 military Flight Academy candidates who underwent medical evaluation in the IAF Aeromedical Center between June 2016 and March 2018. For each disqualified candidate, we examined the cause or causes for disqualification divided into categories.RESULTS: Out of 3281 Flight Academy candidates, 519 candidates (15.8%) were disqualified. The most prevalent cause for disqualification were ophthalmological conditions, which constituted more than half of the disqualifications (55.0%). Among the ophthalmological conditions, nonsatisfactory visual acuity constituted more than half (57.4%). The following most prevalent causes were asthma (7.9%), allergic rhinitis (7.3%), renal and urinary conditions, and otolaryngologic conditions (5.2% each).DISCUSSION: The leading cause for disqualification of Flight Academy candidates was ophthalmological conditions, similar to other air forces. Our findings warrant an ongoing review of criteria for disqualification.Groner O, Frenkel-Nir Y, Erlich-Shoham Y, Shoval G, Gordon B. Medically disqualifying conditions among aircrew candidates. Aerosp Med Hum Perform. 2022; 93(4):384–389.

BACKGROUND: High +G_z exposure is known to cause spinal problems in fighter pilots, but the amount of tolerable cumulative +G_z exposure or its intensity is not known. The aims of this study were to assess possible breaking points during a flight career and to evaluate possible determinants affecting pilots’ spines.METHODS: Survival analysis was performed on the population who started their jet training in 1995–2015. The endpoint was permanent flight duty restriction due to spinal disorder. Then the quantified G_z exposure and possible confounding factors were compared between those pilots with permanent flying restriction and their matched controls. Cumulative G_z exposure was measured sortie by sortie with fatigue index (FI) recordings. FI is determined by the number of times certain levels of G_z are exceeded during the sorties.RESULTS: The linear trend of the survival curve indicates an annual 0.86% drop out rate due to spinal problems among the fighter pilot population. A conditional logistic regression did not find any difference in the FI between cases and controls (OR 0.96, 95%CI 0.87–1.06). No statistical difference was found for flight hours, a sum of intensive flying periods, fitness tests, or with nicotine product use. Additionally, a maximum +G_z limitation without airframe restriction was assessed and is presented as a useful tool to manage loading and developed symptoms.DISCUSSION: No particular breaking point during follow-up or individual factor was found for G_z induced spinal disorders. The results of the study outline the multifactorial nature of the problem. Thus, multifactorial countermeasures are also needed to protect pilots’ health.Sovelius R, Honkanen T, Janhunen M, Mäntylä M, Huhtala H, Leino T. +Gz exposure and flight duty limitations. Aerosp Med Hum Perform. 2022; 93(4):390–395.

INTRODUCTION: Optic disc edema has been well documented in astronauts both during and after long-duration spaceflight and is hypothesized to largely result from increased pressure within the orbital subarachnoid space brought about by a generalized rise in intracranial pressure or from sequestration of cerebrospinal fluid within the orbital subarachnoid space with locally elevated optic nerve sheath pressure. In addition, a recent prospective study documented substantial spaceflight-associated peripapillary choroidal thickening, which may be a contributing factor in spaceflight-associated neuro-ocular syndrome. In the present article, based on the above, we offer a new perspective on the pathogenesis of microgravity-induced optic disc edema from a choroidal point of view. We propose that prolonged microgravity exposure may result in the transudation of fluid from the choroidal vasculature, which, in turn, may reach the optic nerve head, and ultimately may lead to fluid stasis within the prelaminar region secondary to impaired ocular glymphatic outflow. If confirmed, this viewpoint would shed new light on the development of optic disc edema in astronauts.Wostyn P, Gibson CR, Mader TH. Optic disc edema in astronauts from a choroidal point of view. Aerosp Med Hum Perform. 2022; 93(4):396–398.