When the teeny, tiny airways are the problem

I don’t want to brag or anything, but I have stellar lung function. (Despite this, Dia is curious if I may have small lungs like she does due to us both being premature) With that said, my small airways numbers are sometimes a bit lower than my otherwise stellar FEV1.

Lung function tests

In the midst of the yellow zone is when I contemplate things like this—though Dia and her science-y brain want to know more about my asthma all the time. During my most recent flare—it’s been a good while since I’ve had such a persistent, days-long flare, I was mildly, annoyingly short of breath. Near the end of the second day, I finally decided to check my peak flow in the late afternoon. 93%. 93% and I have been short of breath for two days. This is why peak flows are not always reliable: they are a good tool sometimes, but you really have to go with how you feel even if the numbers don’t show it. My suspicion was that the breathlessness was being caused by small airway inflammation when I am feeling somewhat cruddy—peak flows don’t measure these teeny, 1 to 3 millimeter airways. The high peak flow confirmed my suspicions, and confirmed my inclination prior to checking to just go on how I felt. I’d love to be able to get a sense of these small airways numbers—measured as FEF 25-75—at home, although I realize the limitations in this, that these numbers are not very reliable and can be very technique dependent.

A hypothesis

Because of my inability to find objective data (such as a FEF 25-75 reading), “the teeny, tiny airways are the problem” hypothesis is just that: a hypothesis. The thing with flares like this, for me, is that they are extremely annoying, they aren’t severe. I’m short of breath, and my lungs feel generally annoying, but symptoms are semi-tolerable. This is the feeling, for me, that leads me to believe it’s my small airways. But because it’s a nagging sort of mild breathlessness, it doesn’t provoke as intense of action from me as more intense symptoms do. On day 2 I upped my meds (and kept them up for the next five-plus days), and on day 3, at the advice of a friend (who is a respiratory therapist and reminds me of smart things that I should remember myself), I started doing Ventolin every four hours to help break the flare—it took a few days, but between this and increasing my Qvar, I think this is what ultimately helped.

Inhaler particle sizes

Again, just a theory, but here’s why: particle size. As mentioned above, our teeny tiny airways—bronchioles—range from 1 to 3 millimeters in size. Inhaler particle sizes are measured in micrometers also called microns (μm)—each particle of Ventolin is 2.07 μm1—Qvar is even smaller, 1 μm1. An airway is 1000 to 3000 μm (and are, remember, narrowed when asthma symptoms are occurring)2, so the medicine has more than enough space to get through—the smaller the particle, the better chance it has to get as deep in as it needs to, and then deposit (rest) on the airway surface and bind so it is able to begin its therapeutic (medicinal) effect in the airways.3 This is why small particles are important—but why it’s also important they are not too small that they just keep floating around and get exhaled.3 Because Qvar has a smaller particle size than other inhaled steroids at about 1.1 μm—I take mometasone HFA as part of a combo inhaler as well, which has a significantly larger particle size of 3.7 μm; Flovent (fluticasone) HFA is somewhere in the middle, at 2.4 μm4—I do think that this is perhaps what helped to both keep things mild and help get my asthma back into control fairly quickly.

I’m just about back to normal now after three-plus days of diligent work (while I was on the road, no less!) keeping up with taking Ventolin every 4 hours to try to get things to stay open in my lungs, and increasing my Qvar to beat back the inflammation that was probably present in my lungs. I guess even if I can’t tell objectively that my small airways are the problem, my hypothesis was at least somewhat correct!

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