Asthma severity is more than just a low FEV1

It seems I haven’t done a proper “Breathing Basics” post in almost 8 years. I think this installment might fit under that category.

In browsing through some of the posts on various Asthma support groups, personal blogs, or in chatting with people who have asthma or COPD, I often hear someone refer to, or equate the severity of their particular disease to their FEV1 number. Ok, that’s fair. I even do it here on my own blog from time to time. After all, it’s so much easier to label the entirety of your disease with a percent sign, right? But really, I think we’re throwing this acronym around way too much and placing too much importance on it.

While clinically FEV1 is an important measurement of lung function, lung mechanics alone can’t paint an accurate picture of the severity or burden of ones lung disease, especially if that disease happens to be asthma. If you removed the major asthma components from the equation, most people with a reduced FEV1 would not be notably short of breath unless they over exerted themselves. What makes a low FEV1 potentially dangerous is when you throw asthma into the mix. Having your airways suddenly tighten up and narrow, or develope an infection when your FEV1 is chronically low, doesn’t leave a lot wiggle room should your symptoms get out of control. When you factor things that make you more prone to asthma exacerbations in general, such as age, asthma phenotype, mental health status, limited access to medical care, history of hospitalizations, intubations, NFAs, etc, things can get really bad, really quick.

First though, for those who might not know what the term FEV1 means, let me try to explain it as simply as I can.

FEV1 stand for “Forced Expiratory Volume in 1 second“. Basically, it’s a test to measure how fast and fully you can exhale. in one second. Essentially the lower the FEV reading, the worse your lung function is. Anything below 50% is considered severe and anything below 30 % is extremely severe. On the opposite end, anything over 80% is considered normal.
So why do you need to know how fast you can exhale in one second? Well, because that’s crux of all obstructive lungs diseases, including asthma. Its not about having a hard time taking a deep breath in, but rather the inability to exhale the air out freely and completely. In asthma, it’s the narrowing of the airways by the tightening of the muscles that surrounds them (what we call bronchospasm) and/or inflammation and/or mucus on the inside of the airway that makes it difficult to exhale easily. If the if narrowing or “obstruction” gets bad enough, you start to wheeze, maybe cough, get short of breath… all the fun stuff. This difficulty in getting the air out then makes it more difficult to get the next breath in….. and so on and so on. Before you know it, you’re having a full-on asthma exacerbation.
The spirometry test itself goes something like this: you take a deep breath in and blow it out as hard and fast as you can, for as long as you can, into device called a Spirometer. As you’re blowing, the sensor attached to the mouthpiece of the device records and plots your effort and then extrapolates the first 1 second of that breath measuring how much you blew out. The result will be displayed in liters and also as a percentage of your predicted normal value, based on your age, body size and sex. For example on a recent spirometry test below, you can see my best effort for FEV1 was 0.9 liters or 32% of what would be predicted as normal for me based on my age and height.

The test was then repeated a few minutes later after inhaling 4 puffs of Albuterol to see if there was any change. You can see my FEV1 went up to 35%. Though not a huge increase, this uptick indicates that my airways are at least responding to the drug and that some reversibility is present. I should also mention that most people with mild to moderate asthma will have spirometry numbers that are normal or near normal in between flare ups, while those with more chronic severe asthma and who have significant airway remodeling (lung damage), will probably have numbers that are lower and that don’t improve significant, even relatively good breathing periods.

But that’s not all, on the graphic below you see there’s more being measured here than just FEV1. There are lots of other things being measured. Remember that first second of exhalation? Well how about if we measure the flow rates during the 2nd, 3rd, 4th, 5th or even 6th second into the exhalation? ( Yup it can take me that long to exhale all the air out of my lungs). The flow rates measured after the first second tends to come from the smaller airways in your lungs and is reflected by the FEV25-75%, which is basically the middle of your exhalation. The lower these numbers are, the more severe the obstruction and the less likely they will improve. You can see that my FEV25-75 is only 18% and doesn’t improve.

Weve just scratched the surface on what FEV1 and other Spirometry numbers can reveal, but there instances where we also need to measure actual lung volumes in order rule out other conditions that might either mimic asthma or to rule in ones that might be in addition too asthma. Unlike portable spirometers which are everywhere nowadays, tests to measure lung volumes have to be done in a specially equipped PFT lab and are commonly referred to as “FULL PFTs”. There they can also measure how well oxygen and carbon dioxide are able to transfer between the lungs and the blood stream. These ae known as “Diffusion Studies”.

Below is one of the FULL PFTs I did during my Lung transplant evaluation in 2016. You can see there’s a quite a bit more info in a full test.

On the exercise front there are people I know with COPD who actually RUN marathons. Most are older and aren’t super fast, but they still run them. I know one guy with COPD who’s FEV1 is only 28% who not only runs marathons, but has also completed a Triathlon. As you’re probably aware, Ive completed several full marathons myself; my last one just 4 years ago. My average FEV1 during most of those races was 34%. But, the big difference between myself and those “other” marathoners, is that I can’t run at all. Also, I have severe asthma, not classic COPD, so my disease triggers and tolerances to physical exertion are much different. Attempting to sprint, or even racewalk more than 50 yards can throw me into severe bronchospasm and air trapping, of which I have a hard time recovering from and which could potentially kill me. 4 years later, at age 64 with a current FEV1 that hovers around 30%, I now struggle to walk just 7 miles without gasping for breath. On the bright side though, and unlike my COPD counterparts, my O2 sats rarely drop when I exercise. That’s because asthma is a disease of the airways, not the alveoli where oxygen transfer takes place. So again, even when were talking about exercise and the effects lung function, there’s a lot more involved when we’re comparing FEV1 across different types of obstructive lung diseases.

As far as the “other” factors that contribute to asthma severity, frequency and intensity of symptoms, at least for me, is what makes my lung disease so difficult to endure. Constantly feeling short of breath or having symptoms all the time can really wear you down, both physically and mentally. If you can’t breath right, it’s difficult to sleep, it’s difficult to work, concentrate, play etc. This then leaves your body even more tired and your immune system even weaker. Likewise,the more symptomatic you are, the more medications you’ll probably have to take, and some of those meds have terrible side effects and/or don’t work at all. And if the medications aren’t working, you’re exacerbations or flare ups are likely to be more prolonged or severe. And if they’re more severe, you’re more likely to end up in the hospital, and if they cant get your asthma flare under control there, then you could end up on a ventilator, and that could lead to secondary complications…..and well, I think you get the idea.

Asthma is crappy all by itself and can have a huge impact on the quality of life on the sufferer, but add a reduced lung ( FEV1) from lung scarring and its downright cruel. But even if you’re lucky enough to have a normal or only moderately reduced FEV1 or lung function it doesn’t mean your life with asthma is a picnic either. All these other things can make your life miserable, even if your numbers are normal. In the end, its all about living the best you can with what you have to work with.