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

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

Cardiac output,arterial and mixed-venous O2 saturation,and blood O2 dissociation curve in growing rats adapted to a simulated altitude of 3500 m

Summary In rats adapted to a simulated altitude of 3500 m cardiac output measured at hypoxia by the direct Fick principle was significantly lower than in the control animals (mean values 54.3 ml/min and 69.8 ml/min, resp.). The decrease of cardiac output was accompanied by an increase of arterio-venous O₂ difference and a decrease of stroke volume in the adapted rats. It is suggested that the decrease of cardiac output might be related to the increase of hematocrit. The adapted rats also showed higher arterial and mixed-venous O₂ content (both at hypoxia) and increased O₂ capacity. Arterial O₂ saturation of the animals previously exposed to simulated high altitude hypoxia was significantly higher (67.3% as against 61.2% in the controls). The standard O₂ dissociation curve showed lower oxygen affinity in the blood of the adapted animals but no physiological advantage concerning the transport of O₂ to the tissues was found. In another group of animals the Bohr factor was estimated and no difference was found between rat and human blood.