Altitude sickness refers to a combination of symptoms that can result when you take in less oxygen than your body is used to. This happens when you travel to a high elevation (8,000 feet or higher).
It's commonly believed that there's less oxygen the higher up you go. In fact, the concentration of oxygen in the air is the same on top of a mountain as it is at the beach, but the air pressure is much lower.
The lower the air pressure, the less oxygen you take in with each breath. If your body isn't used to functioning on this amount of oxygen, you may start to feel sick.
Altitude sickness can happen to anyone, regardless of age or fitness level, and some people are simply more susceptible to it than others. People who live at higher altitudes – and those who stay there for a while – get used to taking in less oxygen and do just fine. But those who change elevations quickly, especially when they're being physically active, often have trouble.
There are several types of altitude sickness.
Acute mountain sickness (AMS) is the mildest, most common type. Less common and much more serious forms occur when AMS progresses, or when someone with AMS continues to ascend without giving his body a chance to adjust.
These conditions cause fluid to accumulate in the brain – known as high altitude cerebral edema (HACE) – or in the lungs, known as high altitude pulmonary edema (HAPE).
It's unlikely that your child will suffer from altitude sickness, but if you're planning to travel to higher elevations, you may want to take your time getting there.
If you're driving from San Francisco (at sea level) to Denver (at 5,000 feet), for example, your child probably won't have any trouble with altitude sickness. But if you're planning to fly from a low elevation to an elevation that's 8,000 feet or higher, you may want to take a few days to get there, spending a night or two at an intermediate elevation. Then allow one day for every 1,000 feet you travel beyond 8,000 feet.
If your child has a chronic heart or lung disease, though, or any systemic disease that affects breathing, it's a good idea to check with her doctor before bringing her to a high altitude. Also chat with the doctor if your baby is younger than 6 weeks of age, because babies this young are more susceptible to altitude sickness.