Hypobaric hypoxia (decreased oxygen supply to body tissues due to low atmospheric pressure) caused by exposure to high altitude disrupts sleep. Sleep deprivation is associated with degraded post-sleep performance of neurobehavioral tasks. The lowest altitude at which sleep and/or post-sleep performance are affected is not known. The study hypothesis is that sleep and/or post-sleep performance of neurobehavioral tasks will occur due to hypobaric hypoxia at altitudes of 8,000 or less.

Inclusion Criteria:

• healthy
• age 30 to 60 years

Exclusion Criteria:

• sleep disorders or abnormal sleep patterns
• mood or psychiatric disorders including claustrophobia
• altitude exposure above 5,000 ft in the previous 2 months
• born or raised at terrestrial altitude 5,000 ft or greater
• conditions that would disqualify for FAA Medical Certificate
• acute medical conditions