INTRODUCTION: The emergence of normobaric devices for hypoxia awareness training makes crucial the study of physiological and cognitive effects induced by acute normobaric hypoxia (NH) exposure. Our study aimed to 1) investigate the effects of acute NH exposure on physiological variables and working memory; and 2) investigate the physiological and cognitive effects of oxygen breathing before and after acute NH exposure.METHODS: There were 86 healthy men who were randomized into 4 groups: the Normoxia-Air group (N = 23), whose subjects were breathing air; the Hypoxia-Air group (N = 22), where NH exposure was preceded and followed by air breathing; the Normoxia-O₂ group (N = 21), whose protocol was similar to the Normoxia-Air group, except with the addition of 100% O₂ breathing periods; and the Hypoxia-O₂ group (N = 20), whose participants were exposed to 100% O₂ before and after NH exposure. Working memory was assessed with the Paced Auditory Serial Addition Test. Peripheral oxygen saturation (S_po₂), heart rate (HR), and electroencephalogram (EEG) were recorded.RESULTS: Acute NH exposure induced a classical physiological response (i.e., decreased S_po₂ and increased HR), but not identical to the well-described physiological response to acute hypobaric hypoxia. Acute NH also caused a strong impairment in working memory. Oxygen breathing following NH exposure induced a slowing in the EEG associated with a worsening of working memory performance.DISCUSSION: Acute NH exposure revealed a good surrogate for the classical hypobaric chamber for refresher hypoxia awareness training. Because the association between hypoxia and hyperoxia seems deleterious for the brain, we suggest that NH exposure should be surrounded by air breathing.Malle C, Bourrilhon C, Quinette P, Laisney M, Eustache F, Piérard C. Physiological and cognitive effects of acute normobaric hypoxia and modulations from oxygen breathing. Aerosp Med Hum Perform. 2016; 87(1):3–12.

BACKGROUND: We investigated the effect of exposure to +10.0 G for 4 h on the intraocular pressure and the retina of mice.METHODS: We exposed 10 mice to +10.0 G_z for 4 h by using a centrifugal acceleration test facility for animals. Intraocular changes were compared before and after hypergravity exposure. The eyeballs of the mice were enucleated after measuring the intraocular pressure. Tissue slides of the retina were prepared with hematoxylin and eosin (H&E) for histological examination and immunohistochemical analyses for vascular endothelial growth factor-A (VEGF-A), VEGF receptor 1 (VEGF-R1), VEGF-R2, glial fibrillary acidic protein (GFAP), and glutamine synthetase (GS).RESULTS: The average intraocular pressure was 7.7 ± 0.86 mmHg before the hypergravity exposure and 6.65 ± 0.67 mmHg after the exposure. No histological difference was observed between the retinas in the two groups. The levels of VEGF-A, VEGF-R1, VEGF-R2, GFAP, and GS as assessed by immunohistochemistry were increased in the group exposed to hypergravity compared to the control group.DISCUSSION: Repeated exposure to a high level of hypergravity could cause elevation of intraocular pressure and hypoxic damage to the retina.Kim YJ, Chung JS, Jang TY, Kim YH, Chin HS. Hypergravity effects on the retina and intraocular pressure in mice. Aerosp Med Hum Perform. 2016; 87(1):13–17.

BACKGROUND: Hiking and trekking often occur at altitudes up to 12,000 ft altitude. The hypoxia-induced hyperventilation at altitude paradoxically reduces arterial CO₂ (P_aco₂). A reduction in P_aco₂ results in vasoconstriction of the blood vessels of the brain and thus in local hypoxia. The local hypoxia likely affects cognitive function, which may result in reduced performance and altitude accidents. Recent publications have demonstrated that voluntary isocapnic hyperventilatory training of the respiratory muscles (VIHT) can markedly enhance exercise endurance as it is associated with reduced ventilation and its energy cost. VIHT may be useful in blunting the altitude-induced hyperventilation leading to higher P_aco₂ and improved cognitive function.METHODS: This study examined the effects of VIHT, compared to control (C) and placebo (PVIHT) groups, on selected measures of executive functioning, including working memory and processing speed (i.e., Stroop Test, Symbol Digit Modalities Test, and Digit Span Forward) at simulated altitude up to 12,000 ft. Associated physiological parameters were also measured.RESULTS: The Digit Span Forward Test did not show improvements after VIHT in any group. The VIHT group, but not C or PVIHT groups, improved significantly (17–30%) on the Stroop Test. Similarly the VIHT group, but not the C and PVIHT groups, improved correct responses (26%) and number of attempts (24%) on the Symbol Digit Modalities Test. In addition, reaction time was also improved (16%).CONCLUSION: VIHT improved processing speed and working memory during exercise at altitude.Quackenbush J, Duquin A, Helfer S, Pendergast DR. Respiratory muscle training and cognitive function exercising at altitude. Aerosp Med Human Perform. 2016; 87(1):18–25.

BACKGROUND: Helicopter emergency medical services (HEMS) transport critically ill patients to/between emergency care facilities and operate in a hazardous environment: the destination site is often encumbered with obstacles, difficult to visualize at night, and lack instrument approaches for degraded visibility. The study objectives were to determine 1) HEMS accident rates and causes; 2) occupant injury severity profiles; and 3) whether accident aircraft were certified to the more stringent crashworthiness standards implemented two decades ago.METHODS: The National Transportation Safety Board (NTSB) aviation accident database was used to identify HEMS mishaps for the years spanning 1983–2014. Contingency tables (Pearson Chi-square or Fisher’s exact test) were used to determine differences in proportions. A generalized linear model (Poisson distribution) was used to determine if accident rates differed over time.RESULTS: While the HEMS accident rate decreased by 71% across the study period, the fraction of fatal accidents (36–50%) and the injury severity profiles were unchanged. None of the accident aircraft fully satisfied the current crashworthiness standards. Failure to clear obstacles and visual-to-instrument flight, the most frequent accident causes (37 and 26%, respectively), showed a downward trend, whereas accidents ascribed to aircraft malfunction showed an upward trend over time.CONCLUSION: HEMS operators should consider updating their fleet to the current, more stringent crashworthiness standards in an attempt to reduce injury severity. Additionally, toward further mitigating accidents ascribed to inadvertent visual-to-instrument conditions, HEMS aircraft should be avionics-equipped for instrument flight rules flight.Boyd DD, Macchiarella ND. Occupant injury severity and accident causes in helicopter emergency medical services (1983–2014). Aerosp Med Hum Perform. 2016; 87(1):26–31.

INTRODUCTION: Ultraviolet radiation (UVR) increases with altitude; however, there are a number of other factors which may influence ocular exposure during flight. The aim of this study was to assess ocular UVR exposure of pilots in airline and off-shore helicopter operations on different aircraft types and to compare with exposure in a typical office environment.METHOD: In-flight data were captured on equipment including a CCD array spectroradiometer on five return sector European airline flights and one transatlantic flight from London Gatwick in addition to four helicopter flights from Aberdeen Dyce airport. Further data were collected in an office environment from three workstations during summer and winter months.RESULTS: A wide variation in ocular UVA dose was found during flights. The main factor influencing exposure was the UVR transmission of the windshield, which fell into two distinct profile types. In an aircraft with good UVA blocking properties, ocular exposure was found to be equivalent to office exposure and did not exceed international guideline limits regardless of external conditions or flight time. Most aircraft assessed had poor UVA blocking windshields which resulted in an ocular exposure to the unprotected eye in excess of international guideline limits (up to between 4.5 to 6.5 times greater during one flight). No significant UVB dose was found.DISCUSSION: Pilots should be warned of the potential high UVA exposure during flight and advised on the use of sunglasses. A windshield labeling system would allow the pilot to tailor their eye protection practices to that particular aircraft.Chorley AC, Baczynska KA, Benwell MJ, Evans BJW, Higlett MP, Khazova M, O’Hagan JB. Occupational ocular UV exposure in civilian aircrew. Aerosp Med Hum Perform. 2016; 87(1):32–39.

INTRODUCTION: The current research was to investigate pilots’ visual scan patterns in order to assess attention distribution during air-to-air maneuvers.METHODS: A total of 30 qualified mission-ready fighter pilots participated in this research. Eye movement data were collected by a portable head-mounted eye-tracking device, combined with a jet fighter simulator. To complete the task, pilots had to search for, pursue, and lock on a moving target while performing air-to-air tasks.RESULTS: There were significant differences in pilots’ saccade duration (ms) in three operating phases, including searching (M = 241, SD = 332), pursuing (M = 311, SD = 392), and lock-on (M = 191, SD = 226). Also, there were significant differences in pilots’ pupil sizes (pixel²), of which the lock-on phase was the largest (M = 27,237, SD = 6457), followed by pursuit (M = 26,232, SD = 6070), then searching (M = 25,858, SD = 6137). Furthermore, there were significant differences between expert and novice pilots in the percentage of fixation on the head-up display (HUD), time spent looking outside the cockpit, and the performance of situational awareness (SA).DISCUSSION: Experienced pilots have better SA performance and paid more attention to the HUD, but focused less outside the cockpit when compared with novice pilots. Furthermore, pilots with better SA performance exhibited a smaller pupil size during the operational phase of lock on while pursuing a dynamic target. Understanding pilots’ visual scan patterns and attention distribution are beneficial to the design of interface displays in the cockpit and in developing human factors training syllabi to improve the safety of flight operations.Yu C-S, Wang EM, Li W-C, Braithwaite G, Greaves M. Pilots’ visual scan patterns and attention distribution during the pursuit of a dynamic target. Aerosp Med Hum Perform. 2016; 87(1):40–47.

INTRODUCTION: Night vision goggles (NVG) are linked to increased neck muscle activation and pain. Counterweights (NVGcw) are hypothesized to mitigate these effects. The purpose of this study was to investigate the muscular response to varying helmet loads and postures.METHODS: Volunteering from a representative squadron were 16 male helicopter aviators (pilots, N = 9; flight engineers, N = 7). Subjects performed head movements to assume nine different postures (three directions: left, center, and right, at three different levels: down, level, and up) with four different head loads (no helmet; helmet only; NVG; and NVGcw) in randomized order. Subjects were provided real time visual guidance and feedback while assuming the appropriate posture in a cockpit seat in a laboratory setting. Neck muscle activation was assessed with electromyography (EMG) of four different muscle groups, bilaterally, including the sternocleidomastoid, splenius capitis, and mid and lower trapezius.RESULTS: Two- to fourfold increases in muscle activation were observed in postures to the left (down, level, and up) while subjects wore either the NVG or NVGcw as compared to the baseline of no helmet. This was most prevalent in smaller muscle groups (i.e., the sternocleidomastoid and splenius capitis) as compared to larger muscle groups (i.e., the mid and lower trapezius).DISCUSSION: The use of NVGcw did not decrease neck muscle activity as compared to NVG only, particularly when the head posture moved the field of view below the horizon. This suggests interventions to decrease neck muscle activity and fatigue in military helicopter aircrew using NVG should focus on task specific guidelines with respect to countermeasures.Harrison MF, Forde KA, Albert WJ, Croll JC, Neary JP. Posture and helmet load influences on neck muscle activiation. Aerosp Med Hum Perform. 2016; 87(1):48–53.

BACKGROUND: During commercial air travel passengers are exposed to a low ambient cabin pressure, comparable to altitudes of 5000 to 8000 ft (1524 to 2438 m). In healthy passengers this causes a fall in partial pressure of oxygen, which results in relative hypoxemia, usually without symptoms. Patients with congenital heart or lung disease may experience more severe hypoxemia during air travel. This systematic review provides an overview of the current literature focusing on whether it is safe for patients with congenital heart or lung disease to fly.METHODS: The Pubmed database was searched and all studies carried out at an (simulated) altitude of 5000–8000 ft (1524–2438 m) for a short time period (several hours) and related to patients with congenital heart or lung disease were reviewed.RESULTS: Included were 11 studies. These studies examined patients with cystic fibrosis, neonatal (chronic) lung disease and congenital (a)cyanotic heart disease during a hypoxic challenge test, in a hypobaric chamber, during commercial air travel, or in the mountains. Peripheral/arterial saturation, blood gases, lung function, and/or the occurrence of symptoms were listed.DISCUSSION: Based on the current literature, it can be concluded that air travel is safe for most patients. However, those at risk of hypoxia can benefit from supplemental in-flight oxygen. Therefore, patients with congenital heart and lung disease should be evaluated carefully prior to air travel to select the patients at risk for hypoxia using the current studies and guidelines.Spoorenberg ME, van den Oord MHAH, Meeuwsen T, Takken T. Fitnesss to fly testing in patients with congenital heart and lung disease. Aerosp Med Hum Perform. 2016; 87(1):54–60.

INTRODUCTION: It is expedient to use normobaric hypoxia (NH) as a surrogate for hypobaric hypoxia (HH) for training and research. The approach matches inspired oxygen partial pressure (P_Io₂) at the desired altitude to that at site pressure (P_B) by reducing the inspired fraction of oxygen (F_Io₂) to <0.21 using the equation: P_Io₂ = (P_B – 47) × F_Io₂, where 47 mmHg is the vapor pressure of water at 37°C. The investigator then has at site pressure the equivalent P_Io₂ as at altitude, i.e., the NH exposure is at an “equivalent air altitude.” Some accepted as fact identical signs and symptoms of hypoxia for both conditions. However, those that derived the alveolar air equation showed that the coupled alveolar oxygen (P_Ao₂) and carbon dioxide partial pressures (P_Aco₂) for NH and HH are not identical when P_Io₂ is equivalent. They attribute the difference in alveolar gas composition under equivalent P_Io₂ to a nitrogen dilution effect or, more generally, to the respiratory exchange effect. Those that use NH as a convenient surrogate for HH must concede that physiological responses to NH cannot be identical to the responses to HH given only equivalent hypoxic P_Io₂.Conkin J. Equivalent air altitude and the alveolar gas equation. Aerosp Med Hum Perform. 2016; 87(1):61–64.

INTRODUCTION: Motion sickness is often provoked by oscillatory translational (linear) acceleration. For humans, motion frequencies around 0.2–0.3 Hz are the most provocative. A current explanation for this frequency band is that it spans a region of maximum ambiguity concerning the interpretation of vestibular signals. Below 0.2–0.3 Hz, linear accelerations are interpreted as ‘tilt’, whereas at higher frequencies accelerations are interpreted as ‘translation’, i.e., linear motion through space. This is termed the ‘tilt-translation’ hypothesis. However, the origin of this particular frequency range is unclear. We investigated whether the differential perceptions of oscillations at different frequencies derives from the biodynamics of active self-initiated whole body motion.METHODS: Video-films were taken of subjects running slaloms of various combinations of lengths/amplitudes to provoke a range of temporal frequencies of slalom (reciprocal of time to run a cycle).RESULTS: The usual tactic for cornering at frequencies <0.25 Hz was whole-body tilt, whereas >0.4 Hz lateropulsion of the legs with torso erect was observed. Between these frequencies subjects showed variable tactics, mixing components of both tilt and lateropulsion.CONCLUSIONS: This uncertainty in selecting the appropriate tactic for movement control around 0.2–0.3 Hz is the possible origin of ‘tilt-translation’ ambiguity. It also follows that externally imposed motion around these frequencies would challenge both perception and motor control, with the consequence of motion sickness.Golding JF, Gresty MA. Biodynamic hypothesis for the frequency tuning of motion sickness. Aerosp Med Hum Perform. 2016; 87(1):65–68.

BACKGROUND: We report what may be the first evidence-based report of a retinal laser injury to a pilot during commercial flight from a laser device on the ground. Given the significant subjective (blind spot) and objective evidence of focal retinal damage, coupled with the distance involved, we suspect the laser had a radiant power of several watts, known to be injurious to the human retina.CASE REPORT: An airline pilot presented to our department complaining of a blind spot in the upper left area of his visual field in the right eye (right supero-nasal scotoma) following exposure to a laser beam while performing a landing maneuver of a commercial aircraft. At around 1300 ft (396 m), a blue laser beam from the ground directly entered his right eye, with immediate flash blindness and pain. Spectral domain ocular coherence tomography highlighted a localized area of photoreceptor disruption corresponding to a well demarcated area of hypofluorescence on fundus autofluorescence, representing a focal outer retinal laser injury. Fundus examination a fortnight later revealed a clinically identifiable lesion in the pilot’s right eye commensurate with a retinal-laser burn.DISCUSSION: The case reports highlights the growing threat to the ocular health of airline crew and, potentially, passenger safety due to the lack of regulatory oversight of high powered laser devices obtained from the internet. We strongly believe high powered handheld laser devices should not be in the possession of the general public.Gosling DB, O’Hagan JB, Quhill FM. Blue laser induced retinal injury in a commercial pilot at 1300 ft. Aerosp Med Hum Perform. 2016; 87(1):69–70.

INTRODUCTION: Aeromedical evacuation of patients affected by severe infectious diseases inside an aircraft transit isolator (ATI) system is at potential risk of motion sickness (MS). A test flight was then conducted to quantify this risk during the transfer of an Ebola patient from West Africa to Italy.CASE REPORT: A mannequin was inserted inside an ATI and instrumented to provide acceleration parameters throughout the test flight. The analysis of the data predicted a MS incidence of about 2% for a 6-h flight, so the decision to use anti-MS drugs only in selected cases was taken (i.e., those with positive past history of MS, gastrointestinal disorders, or residual carsickness due to previous ambulance run). On this basis, an actual aeromedical evacuation of an Ebola patient was successfully performed without the use of any anti-MS drugs.DISCUSSION: During aeromedical evacuation with ATI systems, the patient’s risk of MS should be evaluated on an individual basis and calibrated according to the specific exposure to motion evoked by the flight platform used. Due to the possible onset of untoward effects, prevention with anti-MS drugs in these patients should be limited to selected cases.Lucertini M, Autore A, Covioli J, Biselli R, D’Amelio R. Motion sickness prediction in aeromedical evacuation of patients with Ebola. Aerosp Med Hum Perform. 2016; 87(1):71–74.

Pearson VM. You’re the flight surgeon: popliteal artery entrapment. Aerosp Med Hum Perform. 2016; 87(1):75–78.

Li HL. You’re the flight surgeon: malaria. Aerosp Med Hum Perform. 2016; 87(1):78–81.