Tuesday, July 26, 2016

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. 


  1. ...I did well when I was using a daily maintenance inhaler (I haven't since April... Change of environment and life changes bring stress and asthma triggers as every asthma sufferer knows. You really need to learn how to control this and it is not difficult. Yes, the long acting bronchodilators are going to be needed most likely for the rest of your life if you have asthma diagnosis confirmed. There are lots of worse drugs. These enable us to exercise outdoors.

    1. I appreciate your guidance. I'm leery of the idea of "medicine for life," which I've watched my father use to treat his asthma for thirty years. What if I lose my health insurance? What if I move to a different country? At the same time, it would be wonderful if something as simple as medicine cured my breathing anxieties. I'm hopeful.

  2. I didn't know such a small percentage difference in SO2 can have that much impact. I need to get one of those toys, more out of curiosity for when I'm up high, since I usually keep my efforts below the point where I think I might encounter issues...

    1. I think it varies for most people, but below 90 percent is officially considered hypoxemia. It seems 85 percent is about where I'm at when I experience dizziness. Before TRT100 in 2011 I did a bit of hypoxic training and occasionally registered as low as 76 percent — that was about the cusp of where I was close to blacking out.

  3. Lots of times I get "gear envy." But, for a pulse oximeter, not so much. You should consider doing a post on all the weird gadgets you have but others (when I say "others," I mean "me.") might not know even exist!

    1. I'm surprised you have't seen a pulse oximeter before. Just about every doctor I've visited uses one for every checkup. I don't think they're intended for use during exercise, but I was curious what the readings would be.

  4. I missed it... what happened to your hand? Why haven't you been on the bike for so long?

    1. Sudden and severe case of carpal tunnel syndrome, then surgery. Working on getting my grip/arm strength back but otherwise recovered from that issue.

  5. Oh no!
    Jill minus joy = no fun. We can all relate to that.
    Hopefully all your answers are right round the corner.
    Do keep blogging, it's very interesting.
    And so glad the hand saga had a happy ending.
    You are getting there!

  6. It would be interesting to compare those readings to similar exercise intensities at lower average elevations. 88 is quite low, my family gets nervous when my dad's O2 sats slip below 90. Now I am wondering how low my 02 sats go on some of my runs...
    Seems like you are getting to a new normal!


Feedback is always appreciated!