Adventures in hypoxemia

 I'll be honest. I thought getting back on my bike was going to be a more joyful experience than it's been. On Monday I set out for a four-hour ride that felt wonderful, at first. But as the miles wore on, I slipped into indifference, which deteriorated further into a dark mood not unlike despondency. I was pretty bummed out. Why? I had no idea. The ride had gone reasonably well. I wasn't particularly strong, but I didn't struggle, either. My hand didn't hurt at all. My breathing was steady and the faucet in my face turned down a few notches even though I've been off antihistamines since last Wednesday. It was a beautiful if slightly warm day, and my route was full of new and beautiful scenery. So what was wrong?

Shortly after returning home, I checked the measurements on our pulse oximeter. My blood oxygen saturation was at 88 percent, with a recovery heart rate of 115. After just a few more minutes that number rose to 90 percent, and within a half hour it was back at my more typical resting measurement, 94 percent. My mood had vastly improved as well.

 In general, blood oxygen levels below 90 percent are considered low. During exercise, dips below 90 percent can indicate a maxed-out effort, which is typically what forces people to slow or stop because they're "out of breath." I've experienced this, but I also seem to be adapting to lower oxygen levels. Now I wonder how much time I'm spending in the 80s, without realizing it. I don't feel great but I also don't feel terrible, so I keep going. But it can't be good. Less oxygen is never good.

After the weird bike ride, I set out today to test my blood oxygen levels during a six-mile run to Bear Peak. I realize this is an unscientific experiment, but I thought it would be interesting to compare the numbers to how I felt:

I checked the oximeter ten or eleven times during the run, and took photos of the readings. For some reason a dark strip obscured the screen in most of the photos. I'm not sure why. So I'm only posting the photos where I remember the numbers. This is from mile 1.5. Oxygen saturation was 89 percent, heart rate in the 150s. For the most part, I felt fine.

 This was the lowest reading I saw, and only briefly, about halfway through the steep climb. Mile 2.8. Oxygen saturation 86 percent. I was beginning to feel dizzy and would have stopped soon to catch my breath anyway. I don't remember my heart rate at the time.

 At Bear Peak, after resting for about two minutes. Mile 3. Oxygen saturation 92 percent, heart rate 136.

Shortly after returning home from the six-mile run. Again, I felt a bit down in the dumps immediately afterward. But this run was only 90 minutes long, so time spent at low oxygen levels was minimal. I perked up quickly. (A cold soda helped.)

Blood oxygen saturation is typically lower at high altitudes, so my resting readings of 94-96 percent are right around normal. Still, I worry about those dips during exercise. Operating at lower blood oxygen may be harmful to my organs and brain. But I'm already working at what I consider moderate intensities. My heart rate would indicate this as well. If I go much easier, I'll have to give up cycling and hill-climbing altogether. Maybe become one of those Nordic walkers clicking along a flat bike path with trekking poles.

Anyway, I am going to see an asthma doctor on Wednesday. Since I recently moved, I'm basically back to square one in regard to testing for allergies and lung function, then moving forward from there. I suspect these tests will check out as normal, as I don't have issues while resting. Exercise still seems to be where most of my breathing difficulties arise. So it may take a while to weed out all of the potential causes for shortness of breath and find any real solution. It does bum me out to realize that I can't be "happy" while exercising because I'm running low on oxygen. And it bums me out more to wonder whether hard efforts might have long-term health implications, and thus become something that I need to avoid.

In the short term, I'm considering working on breathing techniques to maximize my oxygen intake and CO2 exhalation. A combination of altitude, allergies, and past respiratory illnesses may all play a role in my problem. I feel like I did well when I was using a daily maintenance inhaler (I haven't since April), so I'll bring that up with my new doctor. I'm also looking forward to the departure of grass pollen and other allergens that are clogging up my sinuses to such a degree that I haven't had a sense of smell since early June.

On a positive note, after four months off a bike, I was able to ride for four hours on Monday and my butt didn't hurt one bit! It's my one superpower — iron butt — but it rarely lets me down. I'll get this breathing thing figured out. I may start posting about it more often, mainly because it's helpful to have that record to refer back.