What’s in a number?

I still have a hard time believing it, especially the way Ive been feeling this past year, but during my most recent Pulmonary function test a few weeks ago, I blew an incredible FEV1 of 50%!

OK, blowing an FEV1 of only half of normal may not sound like a big deal, but it’s the highest FEV1 Ive achieved on a PFT in nearly 10 years. Actually, I did do a 50% back in 2009 during one of my SARP PFTs, but we were unable to replicate it during the rest of test, so it got averaged into the other numbers and I ended up with a 43%. Like the other, we’re chalking up this most recent aberration to lots and lots of bronchodilators and steroids consumed in the hours and days leading up to the test, which btw was performed on the day I was discharged from the hospital during my most recent stay in December.

Anyway, one of the reasons I decided to devote a blog post to this single PFT number, is because it serves as an important reminder( and one which I often forget), that PFTs dont always correlate with asthma severity and/or symptoms. Airway inflammation is not always reflected in PFT numbers. Though rare, there are some individuals with severe asthma who actually have normal or near normal PFTs in between flares. Additionally, PFTs, especially flow rate readings, are very fleeting and can change from hour to hour. They’re basically a snapshot of what’s happening in the lungs at that the time the test was done. Variability and reliability of PFT results can also be affected by non-respiratory factors, such as patient effort during the test, chest wall and muscle strength, cardiac problems, pain, even anxiety.

Asthmatics such as myself who have terrible baseline PFTs, are usually those who have had the disease continuously for many years, have had numerous severe exacerbations and have some degree of airway remodeling and/or lung scarring present. Probably more reliable indicator of small airway obstruction is the FEV25-75 reading, of which mine is only 6-15% of normal , as well as an FEV1/FVC ratio of only 48% . Having said that, Im happy to say that my DLCO is totally normal… actually above normal at 115%, meaning I have no diffusion or oxygenation problems associated with my asthma, unless I’m flaring.

Again, this FEV1 50% reading was probably a fluke, and of course it doesn’t mean that my lung disease is reversing itself, or that I’m any less short of breath, but on a purely emotional level it sure felt good knowing that the continuing downward trend I had expected in my numbers had plateaued and actually went in the other direction for a change…. at least it did for that day.

Alas, since that PFT was done, my FEV1 has gone back down into the high 30’s and low 40’s again. Today it was 41 %. Still better than it was this past summer. I’ll take it!