The High Sierra

For the body, the less dense atmosphere means there is both less oxygen to be taken in, and less partial pressure to push that oxygen into your lungs' cells. The body adjusts with a slightly quickened breathing and heart rate that you can't notice or control. This is the cause of altitude sickness; that quickened breathing blows off more CO, than is normal, and this reduces the acidity of your blood. That change in your blood's pH, becoming more basic, causes the various symptoms of altitude sickness, which can include head-aches, nausea, and lassitude. Bad cases are called "acute mountain sickness" and manifest as edema, meaning trapped water in cells. Both pulmonary edema and cerebral edema are very bad for you, and can be quickly fatal, as in, over a matter of hours. Ordinary altitude sickness is an adjustment problem, and your body will reacidify your blood by natural means, usually within a day or two. Diamox speeds up that process in ways not fully understood. The side effects of Dia-mox, mostly its diuretic effect (lots of peeing) and its central nervous effect (tingling and numbness, especially in fingers and lips) are apparently not directly related to the desired reacidification of your blood One mild altitude effect is a lessened appetite. Some people get ravenous up there, but others don't get as hungry as their exertions should have made them. Pim in the latter group, which can be useful when packing food for a tip. When Tim up there I can only eat about a pound of food a day, minus its water weight.