EEG, ECG and oxygen concentration changes from sea level to a simulated altitude of 4000Â m and back to sea level

In order to describe how high altitude affects the body during a one night stay at 4000 m experiments were performed in a hypobaric chamber and compared to a study on Dachstein (mountain in Austria, 2700 m). Ten subjects had to perform a reaction time task at different altitudes. The EEG and ECG were recorded simultaneously. Additionally, the oxygen saturation of the blood was measured at different altitudes and the subjects filled out a Lake Louise questionnaire that describes the degree of altitude mountain sickness (AMS). After elevation from 134 m to 4000 m in the hypobaric chamber heart-rate increased from 68.9 bpm to 81.6 bpm, RMSSD (root mean square of squared differences of adjacent heart beat intervals) decreased from 54.3 ms to 33.3 ms, the LF/HF ratio increased from 2.5 to 3.9 and oxygen saturation decreased to 82.7% after 11 h at 4000 m altitude. The Lake Louise Score (LSS) reached 3.4 after one night at 4000 m. EEG beta activity between 14 Hz and 18 Hz was attenuated at 4000 m and also after return to 134 m. The results indicate that the subjects were not able to adapt to 4000 m within 12 h in the hypobaric chamber. Even after 1 h after the return to 134 m all parameters are still affected from the night at 4000 m altitude. ECG and EEG changes are in line with results obtained at 2700 m height at Dachstein.