title: Acute hypoxic hypoxia and isocapnic hypoxia effects on oculometric features.
abstract: BACKGROUND
  Visual performance impairment after hypoxia is well recognized in military and civilian aviation. The aims of this study were: 1) to assess oculometric features such as blink metrics, pupillary dynamics, fixations, and saccades as cognitive indicators of early signs of hypoxia; and 2) to analyze the impact of different hypoxic conditions ["hypoxic hypoxia" (HH) and "isocapnic hypoxia" (IH)] on specified oculometrics during mental workloads.
  
  
  METHODS
  Oculometric data were collected on 25 subjects under 3 conditions: normoxia, HH (8% O2 + balance N2), and IH (7% O2 + 5% CO2 + balance N2). The mental workload task consisted of reading aloud linear arrays of numbers after exposure to gas mixtures.
  
  
  RESULTS
  Blink rates were significantly increased under hypoxic conditions (by +100.7% in HH and by +92.8% in IH compared to normoxia). A faster recovery of blink rate was observed in transitioning from IH (23.6% vs. 76.3%) to normoxia. The percentage change in pupil size fluctuation was increased under HH more than under IH (29% vs. 4.4%). Under HH average fixation time and target area size were significantly higher than under IH. Total saccadic times under hypoxic conditions were significantly increased compared with normoxia.
  
  
  CONCLUSIONS
  These results suggest that oculometric changes are indicators of hypoxia, which can be monitored using compact, portable, noninvasive eye-tracking devices in a cockpit analogous environment to detect hypoxia-induced physiological changes in aircrew. Comparative results between HH and IH support the potential role of carbon dioxide in augmenting cerebral perfusion and hence improved tissue oxygen delivery.
authors.forename: Jan
authors.initials: J
authors.lastname: Stepanek
authors.forename: Gaurav N
authors.initials: GN
authors.lastname: Pradhan
authors.forename: Daniela
authors.initials: D
authors.lastname: Cocco
authors.forename: Benn E
authors.initials: BE
authors.lastname: Smith
authors.forename: Jennifer
authors.initials: J
authors.lastname: Bartlett
authors.forename: Marc
authors.initials: M
authors.lastname: Studer
authors.forename: Fabian
authors.initials: F
authors.lastname: Kuhn
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Cevette
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001767:Blinking / Q000502:physiology*; D003071:Cognition / Q000502:physiology; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D009483:Neuropsychological Tests; D010865:Pilot Projects; D011680:Pupil / Q000502:physiology*; D012438:Saccades / Q000502:physiology*