mountain sickness

we've got a day to spend in the sunny city of miami florida so i figured i'd use a little of this time for educational purposes... when we land in quito ecuador this evening, we will have made an acent from sea level to 9,350ft elevation - a change in atmospheric composition, or rather gas concentration, that puts a bit of stress on our bodies. at sea level we breath easy on air that is 21% oxygen, more than adequate in the dense air in portland or miami, but with altitude air density decreases, and though the percentage of air that is oxygen remains at 21, the concentration of all gases that make up air decrease. when inadequate oxygen is available to meet our body's demand, respiration is stimulated and we begin to breathe faster (tachypnea, in medical lingo). the problem is, to inhale more oxygen you must have a compensatory increase in the co2 you are exhaling. metabolically, losing co2 shifts the balance of reactions that happen within your body and more of the protons in your blood are converted to make more co2 to replace what is being lost. this causes what we call a respiratory alkalosis, or metabolic derangement resulting in less acidic blood. your body doesn't like this. your kidneys have the ability to compensate by excreting more bicarb while hanging onto protons, which can re-acidify the blood. however, the kidneys are slow to compensate and so we speed this process with the help of pharmaceuticals, namingly acetazolamide, which wastes bicarb in the urine and facilitates blood acidification, correcting the aforementioned metabolic derangement. but why do we care if our blood is a little low on protons? well it is more the body's somewhat panicked response to inadequate o2 intake that gets us into trouble. the blood vessels in brain vasodilate and get leaky, causing the high altitude cerebral edema that gives you headaches, makes you nauseous, and could feasibly kill you if it got bad enough. and the lungs too can fill with fluid, high altitude pulmonary edema, which i've experienced on top of middle sister and found pretty darn unpleasant. what we're hoping for, however, is symptoms no more severe than a saturday morning hangover. on that note i think i'll take my next dose of acetazolamide.