Comparison of hypobaric hypoxia symptoms between a recalled exposure and a current exposure

Abstract

Background Aircrew members are required to attend hypoxia awareness training regularly to strengthen their memory of their personal hypoxia symptoms by undergoing training inside a hypobaric chamber. The aim of this study was to examine the association between hypoxia symptoms experienced during two training sessions that were 4 years apart. Methods This was a crossover study to compare hypoxia symptoms and self-reported physiological effects of trapped gas between a previous training session and a current training session in an altitude chamber. The subjects were military crew members who undertook a 25,000feet refresher training course in 2018. We used a structured questionnaire to obtain the target information before and during hypoxia exposure. Data were analyzed using SPSS software. Results A total of 341 trainees participated in this survey and completely filled out the questionnaire. Gastrointestinal tract discomfort caused by the expansion of trapped gas was the main physiological reaction during the previous and current training sessions. Frequently reported symptoms were poor concentration (30.5%), impaired cognitive function (20.5%), visual disturbances (16.4%), hot flashes (15.8%), and paresthesia (12.6%) during both exposures. However, the proportions of participants reporting poor concentration (P = 0.378) and visual disturbances (P = 0.594) were not significantly different between the recalled and current training sessions. The five most common symptoms among the subjects with less than 1,000 flight hours were poor concentration (29.8%), visual disturbance (27.3%), impaired

Hypoxic Hypoxia and Brain Function in Military Aviation: Basic Physiology and Applied Perspectives

“…The primary rationale for HRT is the intentional induction of hypoxia within a safe and controlled environment to: (1) familiarise individuals with their constellation of personal hypoxia symptoms, including order of appearance and intensity; (2) experience the speed of onset and insidious nature of hypoxia; (3) observe hypoxia-induced cognitive and psychomotor impairment in others; and (4) practice using equipment and implementing emergency recovery procedures. An individual’s most prominent symptoms are reported to be consistent for up to 4–5 years for a given hypoxic dose ( Woodrow et al, 2011 ; Johnston et al, 2012 ; Tu et al, 2020 ), which is referred to as their Hypoxic Signature ( Smith, 2008 ). However, not all individuals accurately remember symptoms following hypoxia exposures in training ( Smith, 2008 ; Woodrow et al, 2011 ; Tu et al, 2020 ) and operational ( Files et al, 2005 ) environments.…”

“…An individual’s most prominent symptoms are reported to be consistent for up to 4–5 years for a given hypoxic dose ( Woodrow et al, 2011 ; Johnston et al, 2012 ; Tu et al, 2020 ), which is referred to as their Hypoxic Signature ( Smith, 2008 ). However, not all individuals accurately remember symptoms following hypoxia exposures in training ( Smith, 2008 ; Woodrow et al, 2011 ; Tu et al, 2020 ) and operational ( Files et al, 2005 ) environments. Reported hypoxic symptoms during training may also be different to operational environments, which could be due to a reduced capacity for memory recall, as well as differences in hypoxic dose, environmental conditions and biological variation.…”

Contributions of Hypoxia-Awareness Training to the Familiarization of Personal Symptoms for Occupational Safety in the Flight Environment

“…From the literature review, it can be seen that the results demonstrated that there were variable orders and frequencies of hypoxia symptoms during the chamber flights. Nonetheless, the dominant hypoxia symptoms included mental impairment, coordination issues/slowing response, visual changes, lightheadedness/dizziness, and hot flashes [ 9 , 11 ]. Consistent with former findings, the top five symptoms of our survey by their order of frequency were poor concentration, hot flashes, visual disturbance, impaired cognition, and dizziness/lightheadedness inside the chamber.…”

“…In addition, several studies have reported a consistency in hypoxia symptoms between different sessions of chamber training. The main symptoms during hypoxia-awareness training were impaired mentation, visual changes, dizziness/lightheadedness, paresthesia, tingling, and slurred speech [ 9 , 10 , 11 , 12 ]. Currently, refresher training courses are mandatory in many countries (e.g., every three years in Saudi Arabia, and every five years in New Zealand and the United States) [ 13 ].…”

Analysis of Altitude Hypoxia Training and In-Flight Hypoxia Events among the Helicopter Aircrews

“…Among the military helicopter aircrews, our findings displayed the dominant hypoxia symptoms overlapped with those formerly reported were visual, cognitive impairment, difficulty concentrating, tiredness, and air hunger at this current exposure of 5486-m (18,000-ft) chamber flight. However, several researches identified that, the main hypoxia symptoms at the simulated altitude above 6096 m (20,000 ft) were mental impairment, coordination off, visual disturbance, lightheadedness/dizziness, and hot flushes [10,19]. There were two potential reasons to explain this slight disparity of dominant hypoxia symptoms between the different altitude exposures.…”