Does the higher heart rate have anything to do with getting a light headache (or more) at altitude?
Great question Q.
Lots of factors on plain AMS headache, and its ultimate manifestation as HACE. Some of these are:
*increased cerebral blood flow as the arterial vasculature dilates in response to falling O2, hyperventilation, and resultant falling CO2.
* mechanical shifts in fluid/edema. This occurs in many parts of the body. Swelling in the brain is, well, cerebral edema. Some parts of the brain like corpus callosum are more susceptible than others. Not completely understood.
* humoral change (not funny, but meaning hormonal or other metabolic). These cause shifts between extracellular and intracellular fluid/electrolye balance.
* Size of cranium! There has been suggestion that those with more space in their skulls may have less risk from swelling. I am not making this up.
* faster heart rate? (your question). If you have a headache for any reason, AMS or otherwise, the faster pounding aggravates it. Think of a pulsating mass of tender brain pulsating faster.
