Always curious about things, earlier this week I did a series of FEV1 measurements on myself. I wanted to see if my dyspnea(shortness of breath)which waxes and wanes throughout the day, would correlate with my FEV1 readings. I took the first reading early in the morning when my breathing is at its best. I blew 38% or 1.2 liters. I wasn’t experiencing any perceivable shortness of breath at the time.
Two hours later I pre-nebbed and did my usual 1.5 mile morning walk. 30 min later when I returned home, I measured my FEV1 again and it was still 38%. I was slightly more short of breath than before the walk but felt better again after my post walk neb treatment. I measured my FEV1 several more times throughout the day, and though I was significantly more short of breath in the evening hours ( like I usually am), my FEV1 remained basically unchanged at around 40%.
The following morning I repeated the same experiment, but this time I did a 4.5 mile walk instead of a one mile walk. When I got home I was notably more short of breath. Surprisingly my FEV1 was still at 38% and remained so most of the day, despite having to take multiple neb treatments to quell my breathlessness. It took almost 24 hours for my breathing to return to baseline.
So this little experiment has taught me several things. First, just like with peak flows, FEV1 doesn’t always correlate with the level of breathlessness a person might experience. You can experience an intensifying level of breathlessness, yet have an FEV1 that’s unchanged following a bronchodilator treatment. I suspect that the increased breathlessness(dyspnea)I was experiencing following that longer long walk was the result of air-trapping, rather than from bronchospasm or airway tightening.
By contrast, the Spirometry reading shown below taken during my SARP study back in February (of 2014), shows how my FEV1 changed after bronchodilators were given. It increased by 12%. In this instance, I remember being moderately short of breath before to the test but hadn’t done any significant walking or any type of exercise that morning. I was however, outdoors in freezing temperatures for a few minutes just prior to the test, so the breathlessness I was experiencing at the time was probably a result of bronchospasm triggered by cold air, rather than air-trapping (or possibly a combination of both).
My FEV1 changes were even more dramatic during a subsequent visit at UCSF a couple weeks later. During that test, my FEV1 shot up from 29% to 50% after 8 puffs of Albuterol. I felt mildly short of breath prior to that test but had not walked in nearly 2 weeks (I had just been discharged from an asthma hospitalization and was on tons of prednisone). Once again, the breathlessness I was experiencing prior to that particular test probably had more to do with bronchospasm and/or inflamed airways, than with air trapping.
This experiment also tells me that people with very low baseline FEV1s (below 40%), don’t necessarily feel breathless all the time, unless they’re over exerting themselves for prolonged periods or are actively flaring. I’m not sure about FEV1s below 20%, but more than likely you would have some degree of breathlessness, even at rest if your FEV1 was that low. Hopefully, I won’t have to experiment with the 20’s and teens for a while.
And finally, it tells me that while daily exercise is absolutely crucial for people with lung disease, it’s also important not to overdo it. As I discovered so many times when I was actively training for marathons, it’s not so much the distance you walk, as it is the speed at which you walk that distance. The faster you walk (or run, if you’re able), the faster you breath. The faster and deeper you breathe, the less time your airways have to empty out before the next breath in. If you have a chronic obstructive disease like asthma, this inability to exhale completely can result in excessive air trapping, which can make you noticeably more short of breath, despite an unchanged FEV1.