Nan and Claire

Humans have an affinity to climb. Irresistibly we are pulled, like iron filings to a magnet, by perches, multi-branched trees, hilltops, mountain peaks, observation towers and even through the hierarchy of a job career to “reach the top.”  Many biologists and evolutionary scientists would argue that gaining elevation offered early savanna-dwelling humans a vista to watch for game or approaching threats. Such an advantage, science argues, was so desired for survival that it remains inexorably locked in our conscious. In the past castles and forts were built with commanding views. Today, prime house building sites are often sited high with grand views. Architects continue to defy limits in designing skyscrapers that stretch towards the stratosphere.

Higher and higher. . . . let’s just go a little higher.

Those six words, “Let’s just go a little higher” are powerfully seductive. Over the past few years, when Nancy and I have returned to the Yukon Territory and it’s seemingly infinite crop of peaks, we have often had our day hikes stretched into more hours than planned.   Oftentimes the beckoning siren call of an adjacent higher vista, next to the one we have just climbed, commands our attention. We confer our maps, watches, energy levels and then, more often than not, go for it. More than once we have raced darkness back to our vehicle. That means in the land of the midnight sun, we have wearily come off a hike close to midnight.

In my last blog entry, Tough Efforts, I addressed a recent trekking trip in the Peruvian Andes and the challenges of high elevations. Someone was asking me for more detail about what happens when you climb to elevations that tax the body. So here is my attempt.

First, some basic atmospheric science. In the lower realm of the atmosphere, where we live, there are roughly a dozen gases that mingle together like an invisible, but critical gaseous soup. But two, nitrogen and oxygen, make up approximately 99 percent of the mix.(Note that carbon dioxide is not in the top two, but it has been increasing at rather astonishing rates in the past two centuries, hitting 400 parts per million, for the first time in likely 2 million years. Stay tuned for  some gnarly climate change that is changing the biosphere.)

The atmosphere is an ultra-thin layer of gases that surround the earth. If the earth were the size of a basketball, the atmosphere would be the equivalent of a thin piece of tissue paper. But that thin layer of gases make life possible for us. And as that is not amazing enough, the very mix of gases is what is really critical for us. Most important for our survival is oxygen and that is possible only because of the gift of photosynthesis, the production of oxygen from green plants.

An important property of air is that it has weight. It’s weight can be measured with a barometer and is referred to as barometric pressure. Basically, as one climbs higher,  there is less air, consequently less air pressure.  Our lungs depend on that air pressure to function properly. During periods of very low air pressure, the vacuum that is normally experienced to force the breath to the lungs, barely exists and consequently the air barely seeps in. And if it doesn’t get to our lungs, it fails to get picked up by red blood cells and there is ultimately less oxygen reaching the brain. In a sense, the oxygen-starved brain sends out an alarm to the lungs and heart to work harder. So you start to breathe deeper and your heart begins to race to get oxygen to the brain. (For further, more detailed reading on the subject, I highly recommend you read Surviving the Extremes: A Doctor’s Journey to the Limits of Human Endurance by Kenneth Kamler, M.D.)

You can experience the same phenomenon of oxygen deprivation simply by exerting yourself to the max. There is no need to climb above 14,000 feet, simply try running up several flights of stairs as fast as you can and witness the heaving of your lungs as they work hard to bring oxygen comfort to your brain.

Amazingly we can climb to extremely high elevations if we do it very slowly and acclimatize ourselves gradually to low oxygen concentrations. That is why climbers who tackle Mt. Everest, must do so over a period of time that allows a slow ascent. To do otherwise will kill them.

Perhaps the euphoria, the ecstatic giddiness, I feel when I reach the top of a hilltop or peak is simply because of my oxygen depleted brain. And here I thought it was something more divine than simply biology.

Filed under: Uncategorized