I just read through an article written in 2007 today that found specific features in scalp EEG data, measured at moderate altitude, might predict the occurrence of AMS. You can download the study from the web if you have access to PubMed. I have put the abstract and title of the article at the bottom of this blog entry.
In their study, the authors investigated AMS in relation to brain function, cerebral blood flow, and end-expiratory CO2 and found effects related to AMS in the right-hemisphere scalp EEG. Supportive of this EEG finding are correlated changes in expiratory CO2 and an increase in cerebral blood flow velocity in the right middle cerebral artery.
Notably, changes in the EEG that were determined to be related to AMS occurred before changes in cerebral blood flow and end-expiratory CO2. (Significant changes in the EEG occurred before changes in the cerebral blood flow and end-expiratory CO2.) Hence, changed EEG at moderate altitude might be a good way to identify who will get AMS at high altitude.
While the study showed some encouraging results, the study also has some weaknesses that can be addressed with some replication and some data processing modification. The main weaknesses of the study are: (1) the low number of participants that participated in the study beginning to end (22, at most) and (2) the low significance threshold of 0.05 (for the number of comparisons) that was used. In addition, data plotted in the paper show that for a few participants, the effect of altitude on the EEG was in a direction that was inconsistent with the group. This inconsistency could be artefactual in nature and could arise for a number of reasons unrelated to brain function. A replication of this study would add weight to these findings and offer an opportunity to investigate EEG processing methods that are less susceptible to noise.
Hence, it is worthwhile to do further investigation of EEG as a predictor of AMS in various circumstances, at a variety of altitudes, and investigate how varied training regimes prior to ascent modulate the likelihood of occurrence of AMS.
The abstract and author information obtained from PubMed is given below.
J Neurol. 2007 Mar;254(3):359-63. Epub 2007 Mar 7.In their study, the authors investigated AMS in relation to brain function, cerebral blood flow, and end-expiratory CO2 and found effects related to AMS in the right-hemisphere scalp EEG. Supportive of this EEG finding are correlated changes in expiratory CO2 and an increase in cerebral blood flow velocity in the right middle cerebral artery.
Notably, changes in the EEG that were determined to be related to AMS occurred before changes in cerebral blood flow and end-expiratory CO2. (Significant changes in the EEG occurred before changes in the cerebral blood flow and end-expiratory CO2.) Hence, changed EEG at moderate altitude might be a good way to identify who will get AMS at high altitude.
While the study showed some encouraging results, the study also has some weaknesses that can be addressed with some replication and some data processing modification. The main weaknesses of the study are: (1) the low number of participants that participated in the study beginning to end (22, at most) and (2) the low significance threshold of 0.05 (for the number of comparisons) that was used. In addition, data plotted in the paper show that for a few participants, the effect of altitude on the EEG was in a direction that was inconsistent with the group. This inconsistency could be artefactual in nature and could arise for a number of reasons unrelated to brain function. A replication of this study would add weight to these findings and offer an opportunity to investigate EEG processing methods that are less susceptible to noise.
Hence, it is worthwhile to do further investigation of EEG as a predictor of AMS in various circumstances, at a variety of altitudes, and investigate how varied training regimes prior to ascent modulate the likelihood of occurrence of AMS.
The abstract and author information obtained from PubMed is given below.
Right temporal cerebral dysfunction heralds symptoms of acute mountain sickness.
Feddersen B, Ausserer H, Neupane P, Thanbichler F, Depaulis A, Waanders R, Noachtar S.
Source
Department of Neurology, Klinikum Grosshadern, University of Munich, Marchioninistr. 15, 81377, Munich, Germany. berend.feddersen@med.uni-muenchen.de
Abstract
Acute mountain sickness (AMS) can occur during climbs to high altitudes and may seriously disturb the behavioral and intellectual capacities of susceptible subjects. During a Himalayan expedition 32 mountaineers were examined with electroencephalography (EEG) and transcranial doppler sonography (TCD) to assess relative changes of middle cerebral artery velocity in relation to end-expiratory CO2 (EtCO2), peripheral saturation (SaO2), and symptoms of AMS. We tested the hypothesis that O2 desaturation and EtCO2 changes precede the development of AMS and result in brain dysfunction and compensatory mechanisms which can be measured by EEG and TCD, respectively. Contrary to our hypothesis, we found that subjects who later developed symptoms of AMS between 3,440 m and 5,050 m altitude exhibited an increase of slow cerebral activity in the right temporal region already at 3,440 m. Cerebral blood flow increased in these mountaineers in the right middle cerebral artery at 5,050 m. These findings indicate that regional brain dysfunction, which can be documented by EEG, heralds the appearance of clinical symptoms of AMS.
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