The Caravan of Light will be traveling over high passes in the Himalayas. Experienced mountain travelers understand some of the changes that take place at altitude that can affect health. Here are some of the secrets of high altitude survival.

A simple but critically important fact about traveling to high altitude is that there is less air. If you have ever had anyone hold your head underwater in a swimming pool for longer than you wanted, you know how important air is. Air is made up of a number of gases including nitrogen, carbon dioxide, and oxygen. Your body needs oxygen to survive. Without proper precautions, at high elevation you can feel like you are breathing through a straw. You just don't get enough oxygen. The easiest place to breath is at sea level. That's where you have the most air. As you climb a mountain, the air gets thinner. The chart to the right will give you an idea of how the amount of air decreases as you go up.

Huff and Puff

To understand how to survive at altitude, you need to understand two things:

1. Why we breath
2. How breathing works

Why

Breathing brings oxygen to your cells. Oxygen allows cells to carry on the chemistry that keeps them alive. The second job of breathing is to get rid of waste. The waste in this case is the gas carbon dioxide.

How

When you take a breath, many things happen in your body. Let's start with your blood stream. Think of your blood stream as a real stream. This stream contains blood cells. Those are the little pink guys in the adjacent cartoon. These blood cells start out in your lungs, the dock, where they pick up oxygen (O2), the little yellow suitcases. Then they travel through the blood stream to cells, the greenish clumps. At the cells they drop off their oxygen and pick up that waste gas we mentioned earlier, carbon dioxide (CO2), the purple suitcases. Traveling with the flow of the stream, which is created by a pump, your heart, the red blood cells arrive back at the dock, lungs. Here they drop off their carbon dioxide and pick up another load of oxygen to start the trip again. Must be pretty boring to be a blood cell.

When You Go Up Too Fast

Let's say you rapidly ascend to 10,000 feet (3,050 m). At this elevation, you have 34% less air than you would have at sea level. This means your red blood cells don't have as many oxygen suitcases to pick up and bring to the cells. This is why you breath faster at elevation. It's your bodies way to bring more oxygen into your lungs. If you try to run or do any strenuous activities you'll soon find that even breathing fast won't help. You are simply not able to get enough oxygen.

So why is it that people who live at high elevation don't have this problem? They can run and jump and not feel like they are suffocating. The Sherpa people in Nepal live at very high elevations without a problem. There are climbers who have gone to the top of Everest (without supplemental oxygen) where there's 70% less air. The reason is because their bodies have adjusted. This adjustment includes the production of more red blood cells. More red blood cells means more carriers picking up oxygen and bringing it to the cells. An adjusted body would make the river in the cartoon look crowded with red blood cell boats.

A lack of air does more than simply make you feel tired and out of breath. Going up too fast kills. Your brain and lungs don't like being oxygen starved. Death can occur within hours. So how do you prepare?

Climb Slow

A rapid ascent will get you into trouble. Skiers who fly from sea level to high elevation ski resorts often experience headaches, sleeplessness, and general out-of-breath tiredness for the first few days. It's better to ascend slowly. This is why climbers who ride into base camp on pack mules, quick elevation gain, are more likely to have problems than their slower friends who take several days to trek to base camp. The most important thing you can do to adjust to altitude is to give yourself time. Bodies are smart. Given time they start to make more red blood cells.

Sleep Low

Once above 10,000 feet (3,050 m), many climbers adhere to the following rule: increase your sleeping altitude by no more than 1,000 feet (300 m) a night. Once when Jim was climbing a big mountain in South America, Aconcagua (22,841 feet, 6962 m) he pushed the limits and went 2,000 feet higher in search of a less exposed camp site. That night he had a splitting headache, one of the signs of high altitude sickness. He stayed at this elevation for a number of days while his body adjusted. If the pain had persisted, the recommendation is to descend 1000-3000 feet (305 - 915 m).

Caravan Riddles

• If sea level is 100% air, then what do you think would happen to your breathing if you went to a low point like Death Valley, California which is 282 feet (86 m) below sea level, or maybe the Dead Sea in the middle east where the elevation is 1,360 feet (415 m)below sea level?
• Can you explain why some Olympic athletes go to a high altitude training camp based in Denver, Colorado (elevation 5,280 feet, or 1,609 m)?