One of the major challenges in adapting to high altitudes is that with increasing altitude sleeping quality declines rapidly. Thus, the night sleep can only provide limited to none regeneration. It usually takes a prolonged stay at a constant altitude to adapt sufficiently to the altitude and to have a refreshing night sleep. 1975 Reit et. al showed in their EEG-recordings that the sleep architecture (the regular succession of the particular sleep phases) is disturbed by repeating arousals which occur due to an irregularity in the breathing rhythm.

The purpose of this study is to create a better understanding of the underlying mechanisms that lead to failed acclimatization and AMS, due to sleep disturbance.

Under sea level conditions humans breath between 10 and 12 times per minute. The breathing cycle in high altitude is accelerated. If the conscious breathing control vanishes during sleep a periodic breathing with alternating episodes of hyperventilation and apnea is the result. This circumstance causes repetitive arousals that do not allow a normal sleep pattern. The associated adverse effects are fatigue, slow or failed acclimatization, weakening of the immune system, lack of motivation and the disability to make rational decisions.

Sleep deprivation is a common reason for the abortion of a trip, accidents and severe forms of Acute Mountain Sickness (AMS).

Inclusion Criteria:

• Age: 18 - 80 years
• voluntary participation in an expedition to Mount Kilimanjaro

Exclusion Criteria:

• obstructive or restrictive respiratory disorder
• hemodynamic relevant cardiac defect
• sleep disorder

participants of an expedition to Mount Kilimanjaro