Why is everyone asking 'what is your FEV1%?'...it means nothing

Imagine that in theory your ideal FVC(FEV6) should be 100 for simplicities sake then your minimum FEV1 should be 80 = 80% If your ideal should be 1000 then it would only be 8% -a far cry from the ideal FEV1!

As the FEV1 percentage given is of your 'actual' FVC then if that is only 20% of what it should be you're a lot worse than someone of the same age, gender and height whose FEV1 is 80% of their actual FVC.

SO - you also need to know how far from the ideal your FVC is for any comparison to be made with anyone else's.

My FEV1/FVC is between 25% - 35% of my ideal FVC but is 45% - 53% of my actual FVC.

I have been thinking about this for a few days to try and get my head round it.

Is my belief correct?

Sorry if this doesn't make sense, I know what I mean but am struggling to put it into the right wording.

37 Replies

  • My understanding is that it is a percentage of the predicted, taking into account age, height, gender, and ethnicity. Whether this is a personal or ideal prediction is something I have never thought about. Interesting question.

  • Hi Auntymary,

    Did my question make sense then? I've been pondering on this for a few days and wondering just that as one set makes me moderate and the other moderate/severe.

    I have also come across two different sets of data for the ideal which are quite far apart.

    I'm going to the GPs on Friday so will attempt to ask but my GP is a bit ditsy...shes not the best in the practice so I may have to wait until next week when I go for my PR assessment.

    I've been quit smoking for three weeks now apart from my one slip when I was feeling really low. :) Quite chuffed with myself!



  • Hello Lucky19, you should be very pleased with yourself for stopping 3wks. I used to count the days, then weeks and now it has been nearly 7yrs. and you too will get there, you should be proud of yourself. As for the FEV thing I don`t understand it really,I was told when you blow the long slow one into the spirometery machine, they measure that, then you do the fast short blow as hard as you can, they then divide the short blow number into the long slow number and that gives them the reading.I also am lost with it really.Well done with the non smoking. x xWendy

  • I have no clue either, it's years since I had tests via my consultant, 3 years ago I was told they wouldn't put me through any tests as my lung function was so poor. But, around six years ago I took part in a Glaxo Smith Klyne study into copd (no drugs, just many lung function tests) and was told at some point then was told my lung function was 24% which is much easier to understand I expect. How I wish it was still 24%!. I was referred to the Unit by my consultant at that time.

    PS For anyone in the Manchester (or north west) area, I was paid just under £1,000 for 3 visits a year for 3 years (no drugs, would never volunteer for drug testing) so well worth the trouble. Have just had a look and they are now paying up to £3,000 for studies. Here's the link:-



  • A too give up as my sats are ok but am bushed ... Like hows that work really :O

  • Daz,

    Of course you are bushed, anyone would be after trying to figure out the answers to my hypothetical questions...it's all the brainpower you're using on here! lol


  • Might be right there :)

    Might try being anti social .. Give my lungs a rest all this hyperventalating takes it out of you :)

  • Hey hun,

    I wasn't suggesting you go 'duvet diving', just read the easier blogs for the rest of tonight and come back to the more thought required ones tomorrow!


  • Need scandle to cheer me up .... Take me mind of sore lungs :)

  • After all this talk of spirometry testing Daz, what you really need is a good blow job! ;)

  • Seen That Today On Bizarre Er :) But That Might Of Been Something Totally Different

    Anyway Don't Think That Will Work One Of First Things To Go Must Have Something To Do With Lack Of Oxygen :P

  • Naughty girl Lucky. Lose two house points.

  • That depends who you ask :)

  • Hi people,

    Let's see if I can help you understand this part of the Spirometry Test, or confuse you more.

    This test requires accurate measuring equipment.


    This is your 'Forced Vital Capacity'. Essentially when you are sitting still and breathing slow and deep breaths, and suitably recovered from any exertions you may recently have done. Then take in a deep breath, as much as you can without undue strain, then breathe it out as much as you can, again without undue strain. The volume of that outward breath is your FVC. Usually this is expressed in litres.

    FEV (1)

    This is your 'Forced Expiration Volume in 1 second'. Breathing as described above, take in the deep breath, as much as you can, then breathe out as fast as you can, for 1 or2 seconds, then continue to breathe out until you have to breathe in. The result of this is usually expressed as a percentage. The equipment takes two measurements while you are doing the outward breath. The first is the volume of air you expel in the first second of that breath. The second is total volume of air you breathe out in that breath. The figure you get for FEV(1) is then worked out by taking the volume of that first second's worth of air and expressing it as a percentage of the total volume of that breath.

    Usually the test is done three times with sufficient time between tests for a good recovery. This is to make sure that you are giving a consistent performance so that a bad test can be identified and discounted.

    A normal fit, healthy person would get a result of about 80%.

    As far as I am aware, the current NICE guidelines say that less than 80% is mild

    less than 50% is moderate

    less than 30% is severe

    As a stand alone test, this tends to show the loss of elasticity that a person has suffered, and gives an implication of the amount of scaring and other damage that your lungs have sustained. Where this type of test becomes important is when it is done twice. The first time before you have had any long acting bronchodilators in the day and no short acting within about six hours. After doing the first test, you would be asked to take your short acting bronchodilators, then take the test again after giving the drugs time to work. This gives an indication of how well your drugs work

    There is more to a Spirometry test than I have mentioned here, but I think this covers the question asked.

    If I am wrong in any of this, say so. I am not God, and do make occasional mistakes just to prove it.

    Breathe easy


  • Hi John,

    The only mistake that I can find in here, being particularly pedantic just so that you can be certain that you're human is that 'scaring' is spelt scarring or so I believe. ;)

    I do understand the principle of the spirometry test but what I am trying (obviously not too well) to say is that there are 'ideal' measurements for each of us given gender, ethnicity, age etc. and my ideal FVC is around 350 whereas my 'actual' FVC (or FEV6...being comparable - believe me, I struggle to breath out for six seconds) is only around the 200 mark so an FEV1 of 100 (good for me) would be 50% of my actual FVC but only 21% of my ideal FVC.

    Surely the latter is a more accurate expression of my true lung function - or lack of?

    Does this make more sense as to what I'm asking?

  • Well, as I said before, my lung capacity is around 20%, yet I can breathe out with pursed lips for 15 seconds or more! It has been said many times on here before, whatever your lung capacity or FEV is isn't really important, it's more what you can do with what you've got. There are other people in this forum who are the same or worse than me yet manage to do more, there are also people who have a higher capacity who can do less, so whatever the measurement is doesn't always mean a lot.

  • Hi Libby

    I realise that but I do like to know the ins and outs of what I'm talking about, that's all. Thanks for your input though, always welcome hun.



  • Agreed ... What Can A Say <3 Bit About "it's more what you can do with what you've got" Priceless :P Really

  • Thanks John,

    I am still a bit confused. My last FEV was 73. The COPD nurse said that was above the COPD range which is 70. So she said I didn't have COPD but probably poorly controlled asthma. But if under 80 is mild COPD how can this be? Do I have COPD or don't I? Does anyone know please?

    Am confused.

    Bev x

  • Sorry Bev, I put my reply to Lucky in the wrong place so deleted it!

  • That would depend on the extent of reversibility post bronco dilator use.

  • Kinky :)

  • Huh?????

  • No, not sure what's kinky about using an inhaler...maybe should get my hubby to talk to Daz!

  • Did Daz misread broncho dilator?

  • Not sure, brains in overdrive I think! ;)

  • Hi again John,

    Spent some time reading your seminar speech...impressive. No wonder you're so well versed in all of this however, having read the Barbara Martin - Spirometry handbook for health professionals seems to have given me my answer, the FVC is taken from the 'ideal' for your age etc. etc. and not from your 'actual' FVC which is more to help them to determine the flow pattern to establish whether it is an obstructive, restrictive or mixed breathing pattern thereby aiding in diagnosis of your particular condition.

    Thanks so much for your input though - always welcome a 'professionals' opinion. ;)


  • Thanks for this. :)

  • No problem...though my brain was hurting quite a lot to get through the whole book! ;)

  • hi ive just read thez readings so mine was 67 but didnt get any explanation so am i copd moderate or bit past mild thank u

  • All Very Complex .... What We Need Is Silicon Synthetic Lungs Really PLUG & PLAY Would Be Nicer Than Trying To Work Out The Spirometry Test :O


  • Hmm, think I'll wait until they've got it perfected, after all they might leak like silicone boobs do sometimes!

  • Good Point ... And Or Melt If We Have A Fag aka Cigarette :P

    Was Reading ABout 13 Year Old Boy Died From Smoking Fake Tobacco ... Don't See Public Health Adverts Like That ..... Totally Shocking A No My Aunt As Smoked A Few Tyers .... Can't Trust Out You Buy These Days

    Obviously A Blame Tory Government .... Nope Not Because Am Bias Or Out Like That ..... Its More To Do With Why Not :)

    But Yer A Shall Never Look At Fag In Same Light Again :(

    Thanks For Blast Lucky ... :)


  • OUCH OUCH,, my brain cell is hurting now after reading that tech stuff,,i much prefer,,knackered,, :)

  • Tea and biscuits? ;)

  • Agreed :)

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