Pulse Oximeters and the High-altitude Ultrarunner
Earlier this month ultrarunning queen Courtney Dauwalter was forced to abandon her attempt to run a "supported" FKT (fastest known time) on the Colorado Trail when after 108 hours she developed a bad cough and wheezing. When her crew took her to the emergency room in Leadville, her blood oxygen saturation level was reportedly measured at 70 percent. Arterial oxygen values under 90 percent are considered low.
The doctors ran a full range of tests for HAPE (high altitude pulmonary edema), blood clots, and other severe conditions, but ruled those out and determined she had acute bronchitis.
Last year COROS introduced two GPS watches with built-in pulse oximeters, and although obviously we don't have to deal with blood oxygen saturation issues when we're running in Singapore, at some point we will be traveling again, and some of us will be pushing our limits at high altitude.
Mountain guides, trekkers, and climbers are increasingly using pulse oximeters to monitor their well-being at altitude, and as ultrarunners push farther and higher, mostly at the edge of their physical limits, it makes sense for us to consider taking advantage of technology to stay as healthy and safe as possible.
Now obviously everyone's body is different, conditions before and during every high-altitude endurance effort are different, and there is no magic pulse oximeter reading that will say "stop what you're doing" or "descend immediately". At the same time, there is no reading that can assure you you're not in trouble.
For example, while your blood oxygen saturation will always be low if you're standing atop Mount Everest, a place it has never been smart to linger, an abnormally low reading at 5000 meters could mean your body is having difficulty delivering oxygen to all of its cells, tissues, and organs. In Courtney Dauwalter's case, this was because her acute bronchitis was limiting her ability to absorb enough oxygen when she breathed.
Symptoms of low oxygen saturation levels include shortness of breath, cyanosis (your extremities are turning blue), extreme fatigue and weakness, mental confusion and headaches. Now of course most of these "symptoms" can be classified as "just another day out" for long distance ultrarunners, but you get the idea: use your judgment (and your crew's judgment). As you may imagine, Courtney didn't want to interrupt her Colorado Trail effort to go to the hospital. Her crew insisted.
Pulse oximeters, like all technological devices, are a tool that can and should be used to support experience and good judgment, with the primary goal of getting you back home safely.
The COROS Vertix and COROS Apex Pro have built-in pulse oximeters that provide 24/7 blood oxygen monitoring. Check them out in the shop or online at https://www.rdrc.sg/collections/coros.