Spirometry

[Titch1908]

Had my spirometry today, i have severe asthma. She said that spirometery was 40% of what someone of my age/height etc should be. What does this mean?

[DeanSamson]

Hello a spirometry test is basically the measurement of the amount of breath you can push out in one go. The majority of people with asthma will have a reduced amount. Was your specialist concerned?

[Poobah]

I hope I've understood your question.

The expectation for someone without a lung disease or other obstruction to the wind pipe (e.g. thyroid disorder, vocal disorder) is 80%, therefore any results less than 80% will be considered abnormal, in varying degrees mild to extremely severe). That's 80% of what is expected for the patient's age, height & weight, not a static 80%.

In addition to spirometry I also have blood tests at intervals to monitor IgE & eosinophils (inflammatory markers), various blood cell types and I believe that allergies can also be identified. Sputum is also tested - phlegm contains old lung cells that can give clues to what's going on and infections can also be identified. Less often CT scans and X-rays are also used to pin point diagnosis.

So spirometry is just one test that can be used but is an indication of the severity of your lung restriction. 40% is severe as it's half that of the "normal" expectation of a patient of your age, height, weight.

With targeted treatment with the right asthma meds you should find an improvement in your spirometry and lung function. From here on in, it can identify if a treatment is working sufficiently to improve your lung function.

[JumpJiving]

I'm pretty much a newbie to the world of asthma, mine being diagnosed (without spirometry because even now my GP practice isn't doing it because of the COVID 19 pandemic) 8 months ago, so this is a question (for readers who know more than me) rather than experience - at 40% wouldn't it be normal for CT scan, or at least an X-ray, to be done in case there is something else going on that could be treated? Is there a decision tree / flowchart available that doctors are supposed to follow? Even if nobody answers that here, you might want to ask your GP about a CT scan.

In my own case, peak flow tests are still short of what would be expected after 8 months of inhaler use. By chance, a CT scan being done for something completely unrelated has just shown that I have a collapsed left lower lung lobe, something that I believe neither peak flow tests nor spirometry would identify on their own. From my layperson's perspective, I suspect that collapsed lobe may well explain the peak flow shortfall in my case. The chances are that I have been living with that collapsed lobe for about 20 years (when I had a really bad flu, which my GP said became bronchitis, pneumonia and then pleurisy - the pain was the worst I have ever experienced, which I and the GP had put down to pleurisy, but possibly it was the lobe collapsing - will probably never know). Had that been picked up at the time I imagine it would have been treated at the time, whereas after all this time I doubt there's anything that can be done for it (I'm speaking with new GP about it in a couple of weeks, more in the hope of using the lobe as a reason to get the spirometry done rather than expecting anything to be done about the lobe). That's my situation, but in case there's something unexpected like that, personally I'd be pressing for a CT scan if I had a 40% result. Please don't be scared by this, you probably don't have anything similar, but a scan would confirm.