Working Memory Impairment in Pilots Exposed to Acute Hypobaric Hypoxia

Introduction: During an acute hypoxia exposure, impairment of memory is one of the most frequently reported symptoms, either during hypoxia awareness training of aircrews or after an in-flight hypoxic incident. However, the effects of acute hypoxia on memory have been little studied in laboratory-controlled conditions. Moreover, none of these studies were performed in hypobaric conditions. The main aim of our study was to investigate the effects of acute hypobaric hypoxia on working memory (WM). This study also aimed to find links between physiological measurements and cognitive performance during acute hypoxia exposure. Methods: During hypoxia awareness training, 28 subjects (experimental group) were exposed to a simulated altitude level of 10,000 m (31,000 ft) in a hypobaric chamber, while 29 subjects (control group) stayed at sea level. WM was assessed in both groups with the Paced Auditory Serial Addition Test (PASAT). Peripheral oxygen saturation (S(p)o(2)) and heart rate were recorded. Results: WM was strongly impaired in the hypoxic group. One major finding is that hypoxia highly increased the mean error frequency rate. WM performance decreased linearly with hypoxemia, but S(p)o(2) was weakly predictive of PASAT performance and vice versa. Discussion: WM is impaired by acute hypobaric hypoxia. Given the importance of WM in aircraft piloting and its sensitivity to hypoxia, the PASAT, in association with S(p)o(2) and EEG recordings, could improve both hypoxia training and our understanding of the effects of hypoxia on memory.