Peak Flow Accuracy

I know most of you on here cite your peak flows in relation to how ill you feel, but am I the only one who doesn't seem to have much correlation between symptoms and peak flow reading? Only once, a few years ago, have I had a low reading of 350 and that was when I really felt terrible, but even now when I wake up short of breath and tight Chested I'm still able to get 600-700 which is my normal reading.

Has anyone else had this experience or is it just me? It is starting to make me wonder if this latest flare up is asthma or something else entirely.

10 Replies

  • Not just you, I know the feeling! Also, I've read on here people saying they can have really severe attacks but their PF doesn't always drop for ages.

    I don't have severe attacks but my PF likewise refuses to be helpful which is really quite annoying because it would be so useful if I could use it as a measure. It does sort of respond to how I'm doing but only weakly and it's not very sensitive, so I've had times when I'm feeling rubbish, take loads of reliever and that pushes my PF up but doesn't do much for the symptoms, so if I then go to OOH or something they don't really believe I'm having any issues at all! I do find that if in general I'm not doing so well my PF will be more in the yellow zone and it will take more reliever to push it up, but the doctors who know me have now kind of accepted that my PF may not be the best way for me to measure how I'm doing - though they're still trying to work out what's going on, and it doesn't help that my personal best is 600 while my predicted best is 470!

    Sorry for the ramble, just wanted to show you're not alone in this... Would also add that I used to be able to get even higher readings when feeling rubbish but the consultant watched me do it and said I was practically coughing into it and anyone could get a good reading that way even when struggling. I was also told by one of the adviceline nurses here that PF may not always be an accurate reflection of what's going on as it tends to measure the larger airways so if the smaller ones are acting up it may not show.

  • me too!!!! I wonder if it's because i'm a cougher rather than a wheezer

    Even when i'm at my worst i can still manage 400+ (on the old scale)whereas my normal is around 450 so not a lot of difference, and at that stage my reliever makes little difference to PF. I've found it so unhelpful i've actually given up on measuring my PF and go by symptoms instead

  • Thanks for the replies ladies(?).

    It doesn't help that docs, especially in a and e, listen for a wheeze and the look at peak flow and if both are ok they look as if to say 'what's your problem?'. Very frustrating as it doesn't seem to be the superb indicator they think it is.

  • i can have all the symptoms but still a good peak flow althou if my pf drops really low my symptoms are normally alot worse. but the peak flow helps build the bigger picture of my asthma

  • from what i understand the peak flow is how fast you can breath out not the amount of air you can get into to breath. so if you can puff out your peak flow will be quite good even if your not able to breath properly. Thats my understanding. If my chest feels really tight then my peak flow drops, but not always. I find that I cant talk in sentences sometimes even if my peak flow is reasonable.

  • Yes your peak flow is a measure of how much air you can blow out at speed. It is only *one* measure of lung function and not designed to be used in isolation. Symptoms and other issues are also important to build up the picture. It is not a measure of your lung capacity/how much you can breathe in.

    My peak flow is a very poor indicator of my lung function because I have other stuff going on as well as asthma. My best is 320 (rare), but it doesnt have to drop far before Im in a real mess (I cant go by the usual 80% etc measurements). Sometimes my peak flow can be 300 and Im really breathless (often due to infection, not asthma), other times it drops when Im breathless (more likely asthma).

    Lynda :)

  • Wow! Thanks everyone! I thought it was just me. I am taking my pf religiously and I keep waking up uncomfortable (also due to prednisolone insomnia) and then finding my pf is something really good like 400 now that they've added in montelukast! I also have a bad pain down my chest after doing anything remotely active and although my pf does drop after I've overdone it, I should according to the readings I'm taking, be feeling a lot better than I am. I keep thinking 350? I did a week at work on that and I couldn't do that at the moment.

    There is also that classic of when you present yourself at A&E needing nebs NOW and they take a pf and ask you your best - if you're not around 50% you don't get taken seriously- I got sent to sit in the waiting room when I was almost passing out because I blew 270 and said my best was 475.

    GRRRRRRR! Infuriating.

    But thanks guys - I know I'm not the only one now!

  • my peak flow is 710 since ive been recording in july except ive never had an asthma attack or anything my asthma is really mild but just persistent.

  • OMG a peak flow of 710!? That's amazing, what I would do for that... My best is 330 and that's very rare...

    Lynda :)

  • haha ive just been to the docs again today and topped it with a peak flow of 800 i managed to top the meter !

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