Enhanced cerebral blood flow in acute mountain sickness

Area of Science:

• Physiology
• Altitude Medicine
• Neurology

Background:

• High altitude exposure triggers physiological changes.
• Acute mountain sickness (AMS) is a common condition at elevated altitudes.
• Cerebral blood flow regulation is crucial for brain function under hypoxic conditions.

Purpose of the Study:

• To investigate changes in middle cerebral artery blood flow velocity (MCA-v) during high altitude ascent.
• To correlate MCA-v alterations with the development of acute mountain sickness (AMS).
• To examine the relationship between MCA-v, arterial oxygen (PO2), and carbon dioxide (PCO2) levels.

Main Methods:

• Transcranial Doppler sonography (TCD) was used to measure MCA-v in 23 subjects.
• Measurements were taken at low altitude (490 m) and after rapid ascent to high altitude (4559 m).
• MCA-v changes were monitored daily for 72 hours and correlated with AMS symptoms and blood gas levels.

Main Results:

• MCA-v significantly increased at high altitude, with a greater rise in subjects experiencing AMS (148% of baseline) compared to those without AMS (127%).
• The increase in MCA-v was statistically significant on days 1 and 2 in AMS-positive subjects.
• MCA-v elevation showed an inverse correlation with arterial PO2, particularly on days 2-4.

Conclusions:

• Subjects developing AMS exhibit a more pronounced increase in middle cerebral artery blood flow velocity at high altitude.
• This elevated MCA-v appears linked to lower arterial PO2 levels, suggesting altered cerebral perfusion regulation in AMS.
• The findings contribute to understanding the pathophysiology of acute mountain sickness.