Hypoxia impairs reaction time but not response accuracy in a visual choice reaction task.

We investigated the effect of hypoxia on the reaction time (RT) and response accuracy of pilots performing a visual choice reaction task that corresponded to the scanning of helmet mounted display (HMD) symbology. Eighteen male military pilots performed the task in a hypobaric chamber at two simulated altitudes (92 m and 4572 m) in a single-blinded repeated measures and counter-balanced design. The visual stimuli were displayed in low and high contrast and at a 30- and 50-degree field of view (FoV). We measured the pilots' RT and response accuracy. Using an eye tracker, we measured the pilot's glance time at each stimulus location. Finally, we collected subjective ratings of alertness. The results show that hypoxia increased the RT and glance time. Lowering the stimulus contrast and increasing the FoV further increased the RT, independent of hypoxia. These findings provide no evidence for hypoxia-induced changes in visual contrast sensitivity or visual field. Instead, hypoxia seemed to affect RT and glance time by reducing alertness. Despite the increased RT, the pilots maintained their accuracy on the visual task, suggesting that visual scanning of HMD symbology may be resistant to the effects of acute hypoxia.

Exposure to hypoxia impairs helicopter pilots' awareness of environment.

The purpose of the present study was to determine how hypoxia effects awareness of environment (AoE) in helicopter pilots operating at high altitude. Eight helicopter crews flew two operational flights in a flight simulator while breathing gas mixtures of 20.9% (equivalent to 0 m altitude) and 11.4% (equivalent to 4572 m or 15,000 ft altitude) oxygen in a single blinded, counterbalanced, repeated measures study. Each flight included five missions, during which environment items were introduced that the crews needed to be aware of, and respond to. In the 4572 m simulation, the crews missed overall 28 AoE items compared to 12 in the 0 m simulation (Z = -1.992; p = .046). In contrast, the crews' technical skills were not significantly effected by hypoxia. Remarkably, the majority of pilots did not notice they were hypoxic or recognise their hypoxia symptoms during the simulation flight at 4572 m. Practitioner summary We show that hypoxia has a detrimental effect on helicopter pilot's AoE and alertness. This can lead to an increased risk for flight safety. To mitigate this risk we recommend performing hypoxia training in a flight simulator, developing wearable systems for physiological monitoring of pilots and re-evaluating current altitude regulations. Abbreviations: ANOVA: Analysis of variance; AoE: awareness of environment; CSV: comma-separated values; HDU: helmet display unit; HR: heart rate; IQR: interquartile range; Mdn: median; NTS: non-technical skills; RNLAF: Royal Netherlands Air Force; PPM: parts per million; SpO2: oxygen saturation; SSS: Stanford sleepiness scale; TS: technical Skills.

Flight Performance Aspects During Military Helicopter Flights.

INTRODUCTION: A flight is composed of many flight performance aspects. However, not all of these aspects are equally important for the success and safety of a flight. When investigating the influence of a stressor on flight performance, it is important to understand not only which flight performance aspects are important for the success and the safety of the flight, but also which of these aspects will most likely be affected by reduced alertness.METHOD: A total of 136 helicopter pilots of the Royal Netherlands Air Force (RNLAF) of all qualification levels were invited to participate in a three-round ranking Delphi study.RESULTS: A total of 41 (30%) helicopter pilots completed the first questionnaire round and 20 (77%) flight instructors completed the ranking round. The top ten skills elements comprised seven nontechnical skills (NTS), namely, awareness of the environment, decision making, workload management, stress management, planning and coordinating, general knowledge, and basic fitness; and three technical skills (TS), that is, advanced aircraft handling, flight maneuvers and procedures, and abnormal and emergency procedures. The top three ranked skill elements (awareness of environment, decision making, and workload management) were considered by the flight instructors to be highly influenced by reduced pilot alertness.CONCLUSION: NTS are considered more important and more affected by reduced pilot alertness during operational helicopter flight compared to TS.Steinman Y, van den Oord MHAH, Frings-Dresen MHW, Sluiter JK. Flight performance aspects during military helicopter flights. Aerosp Med Hum Perform. 2019; 90(4):389-395.

Flight Performance During Exposure to Acute Hypobaric Hypoxia.

INTRODUCTION: The purpose of the present study was to examine the influence of hypobaric hypoxia (HH) on a pilot's flight performance during exposure to simulated altitudes of 91, 3048, and 4572 m (300, 10,000, and 15,000 ft) and to monitor the pilot's physiological reactions. METHOD: In a single-blinded counter-balanced design, 12 male pilots were exposed to HH while flying in a flight simulator that had been placed in a hypobaric chamber. Flight performance of the pilots, pilot's alertness level, Spo2, heart rate (HR), minute ventilation (VE), and breathing frequency (BF) were measured. RESULTS: A significant difference was found in Flight Profile Accuracy (FPA) between the three altitudes. Post hoc analysis showed no significant difference in performance between 91 m and 3048 m. A trend was observed at 4572 m, suggesting a decrease in flight performance at that altitude. Significantly lower alertness levels were observed at the start of the flight at 4572 m compared to 91 m, and at the end of the flight at 4572 m compared to the start at that altitude. Spo2 and BF decreased, and HR increased significantly with altitude. DISCUSSION: The present study did not provide decisive evidence for a decrease in flight performance during exposure to simulated altitudes of 3048 and 4572 m. However, large interindividual variation in pilots' flight performance combined with a gradual decrease in alertness levels observed in the present study puts into question the ability of pilots to safely fly an aircraft while exposed to these altitudes without supplemental oxygen.Steinman Y, van den Oord MHAH, Frings-Dresen MHW, Sluiter JK. Flight performance during exposure to acute hypobaric hypoxia. Aerosp Med Hum Perform. 2017; 88(8):760-767.

The effect of an optimised helmet fit on neck load and neck pain during military helicopter flights.

The main purpose of this study was to improve the helmet fit of military helicopter aircrew members and evaluate its effect on the experienced helmet stability (helmet gliding), neck load, neck pain, hot spots (pressure points), irritation/distraction, and overall helmet comfort during night flights. A within-subject design was used over a three-month period that consisted of two consecutive interventions of optimising the fit of the aircrew's helmets: 1) a new helmet fit using a renewed protocol and 2) replacement of a thermoplastic inner liner with a viscoelastic foam inner liner. A total of 18 pilots and loadmasters rated the outcome measures using the Visual Analogue Scales immediately after their night flights, for three night flights in total per measurement period. The optimised helmet fit resulted in a significant decrease in the experienced helmet gliding, neck load and pressure points, a decrease trend in the experienced neck pain and irritation/distraction, and a significant increase in the experienced overall helmet comfort during flight. These results demonstrate the importance of achieving an optimised helmet fit for military helicopter aircrew and that an optimised helmet fit might have implications for both health and safety concerns.