I’m coming to you live from the red desert of St. George, Utah. In case you’re making a list of destinations for a U.S. road trip, this is one city you could skip. I hear you wondering, then why are you there? The prime reason is that it sits at a lower elevation than Zion National Park, where we’ve been visiting.
St. George is about 2,700 feet above sea level (low to moderate altitude) while Zion National Park is at 4,000 feet (moderate altitude) and Bryce National Park is even higher, at 8,000-9,000 feet (high altitude.) After a few days of hiking through the indescribable beauty of Zion canyon, it was becoming increasingly hard to keep my blood oxygen level within a healthy range. (This awareness made possible by a smart watch with a built-in pulse oximeter.) When I found myself and my inhaler enjoying(!) a 2 a.m. cup of tea, it was clear it would be insanely stupid to continue on to Bryce.
The middle of the night is a great time for learning. My adventures with a pulmonary embolism had imprinted the go-to-the-emergency-room blood oxygen level on my brain. I found a handy chart that contextualized that number.
In Zion, my numbers had dipped into, then begun to linger, in the concerning zone.
For those of you watching at home, the Cleveland Clinic sums up blood oxygen in a few sentences: “The amount of oxygen in your blood is your blood oxygen level. Your body needs a certain amount of oxygen in order to function properly, and low blood oxygen levels can lead to serious complications.” Some symptoms of low oxygen saturation include shortness of breath, cyanosis, extreme fatigue and weakness, mental confusion, and headaches.
What does elevation (altitude) have to do with the level of oxygen saturation in your blood?
Altitude is related to air pressure. As we go higher, there’s less atmosphere pressing down on us. As pressure decreases, there are fewer molecules present. (This is called Boyle’s law.) The percentage of air molecules that are oxygen is always the same— 21%— it’s just that at higher altitudes, there are fewer molecules of everything. No matter how you slice it, 21% of a shrinking number of molecules means less oxygen available for breathing.
As a result, the lungs (Our Heroes) have to work harder to get oxygen into the blood. People breathe faster and deeper. Some may feel short of breath (me, wildly waving my hand.) After a couple of days, the body can get used to this. Or not, as I discovered.
There are no hard or fast rules for any of this. Some people hike at elevations above 8,000 feet with little difficulty. And shortness of breath doesn’t necessarily correlate with low blood oxygen levels. As someone with lung function that’s on the lower end of normal, plus asthma (double winner!), I pay attention to dyspnea (the fancy term for “shortness of breath”) and pulse ox levels.
According to the Society of Mountain Medicine, there are three altitude regions:
High altitude = 1500 to 3500 meters above sea level (4900-11500 ft.)
Very high altitude = 3500 to 5500 meters above sea level (11500 to 18000 ft.)
Extreme altitude = above 5500 meters above sea level (18000 ft.)
But if you are coming from sea level (i.e., the 56 feet of my home town) the numerical markers for altitude regions aren’t as significant as the amount of change from lower to higher altitude. In my 2 a.m. learning frenzy, I discovered that the last Zion hike we did added 1,000 feet to Zion’s average elevation. No wonder my lungs hauled me out of sleep in the middle of night….
Which brings us to St. George, where, after a good night’s sleep, I woke with a stellar blood oxygen level.
Could I could have done a little more due diligence before blithely ascending into Utah’s canyon lands? I think that qualifies as a no brainer. (And, yes, you told me so.)
Is the moral of the story that I just should have stayed home?
HELL NO!
The moral I choose is this: decide to live fully, with zest and joy, and then go out and do it.
Otherwise you might miss this:
or this:
Thanks for reading. I hope you’re enjoying some deep breaths of the sweetest air around!