Backcountry Beacon

Andy Chapman above 6,000-meters in the Cordillera Blanca, Peru.

As a result of the lower barometric pressure at high altitude, the air (and the oxygen in it) becomes less dense (fewer molecules per unit of volume), so you cannot get as much of it into your lungs. Have you ever put a bag of chips in your car and then driven over a pass? The bag that was about half full of air will be bursting at the seams by the time you’re a few thousand feet higher. Though the amount of air in the bag hasn’t changed, it’s under less pressure than it was at a lower elevation. That expansion is similar to what’s happening to the air around you when you climb a peak. However, while the atmosphere around you is expanding, your lungs are the same size, so each breath you take has a lower percentage of oxygen than it did at a lower elevation.

As you near the poles, the atmosphere becomes less deep (there’s less distance from sea level to the edge of the toposphere at the poles than there is near the equator). So, comparable air density decreases happen at lower altitudes at the poles than they do at the equator. As a result, altitude changes have larger physiological impacts near the poles. For example, 20,000 feet in Alaska feels higher than 20,000 feet in Peru.

No matter where you are, you have to take more breaths at a higher elevation to make up for the lack of oxygen in your body, so even just walking around feels like you’re running. This lower barometric pressure and decreased oxygen may cause a number of life-threatening illnesses, so proper acclimatization is key on any trip to a big peak. Read More …