Peak Flow - does it work?

Has anyone else found that you can have a tight chest yet no dip in your peak flow. Other times my peak flow will correspond to how I'm feeling but often it just doesn't! and GPs act like its the best thing ever ! If i have a good peak flow whilst I'm in the docs they'll just act like I'm right as rain (and therefore must be absolutely fine outside of the docs too) and send me away. I just don't always feel that it's an accurate measure of how I'm feeling.

17 Replies

  • Ah yes, good oil' peak flow, it barely follows my symptoms either! Can be fine and drop pf, be struggling and pf fine, especially at the gps, its always a good 50 higher there. Added to that I have a high personal best, so even when pf has dropped, its higher/not much less than my predicted.I always struggle to get oral steroids when I know I need them, because of this, and then I always need longer to get over it.

    A lot of people on here have suggested to me that you should record symptoms both when good and when bad and present that to the gp before they get hung up on peak flow.

  • I am so glad other people are finding this. And my pf is always brilliant in the docs!! its like my body is playing with me.

    Yes that's a great idea, I will record my symptoms too.

  • ughh yes, me too! Really not that great a measure and actually my regular GPs get that but the cons is really hung up on it atm which I'm finding very frustrating as I really don't think it necessarily reflects what's going on. It's not just the feeling crappy and having symptoms etc with good PFs either, at times I've felt ok and it's not budged! And recording it shows a kind of general trend that it\s worse when I have a flare, but indvidual readings aren't necessarily always that helpful. Atm I'm doing much better than I was a few weeks ago but PF is defo lower...go figure.

    Cons doesn't go for the symptom/reliever use recording either as I think he thinks it doesn't count unless there's PF to back it up. I can see the need for something objective but at the same time, there are so many of us on here who don't find it reliable that I feel maybe it shouldn't be the be all and end all. I talked to a lovely resp nurse who came to see me in hospital about a month ago (shouldn't have been there according to PF readings apparently!) and she said she had been doing some research as part of CPD on peak flow and all the research she had found suggested it really wasn't that reliable and needs to be used with caution and in conjunction with other things.

    I also have the 'high PB' to contend with so even if it HAS dropped, it can look fine and I get a lot of 'well at that level why does it matter?' (errr, cos if I were a bloke and 600 were my predicted best you probably wouldn't be saying pretty sure the extra, for me, is not spare capacity or why do they use personal bests?)

  • yup i'm another one whose PF doesn't reflect how i'm feeling

    I'm also Cough Variant non-wheezer which isn't helpful as far as some doctors are concerned

    I'm lucky in that i think i'm fairly well controlled and only a couple of times i've felt bad enough for medical attention - although the 1st time i didn't get any attention cos i was away on a pilgrimage and ""didn't want to make a fuss""! Yes i know now it was stupid but i was only 18 and was the youngest (by a lot) on the trip. I just used A LOT of reliever (and cried a lot) over the course of the week that i was there. Once i was home and away from all the smokers i was ok within a week or so.

    The other time i DID go to the dr but he just said double my preventer, which i'd already doubled anyway - my standard dose is 1 puff morning & night so then i was on 4 morning & night and he said i could use my reliever up to every 2 hours and if i was needing it more than that i should think about A&E!

  • peak flows are good for measuring your breathing strength but sometimes after doing these people think cause the peak-flow is showing good results then they should be as thre saying goes right as rain. but sometimes people may feel bad even after doing a peak-flow because there could be other problems and stuff, ( as my partner suffers with bad chest-infections sometimes we end up in the local A&E to be told nothing to worry about its just an imflamed chest bone.

  • Peak flow is not really a good test - it's just easy and portable. It is possible to learn techniques to get a better score, without having any beneficial effect on your asthma. In a full lung function (spirometry test) you would do a Forced Expiratory Volume 1 second (FEV1) test. This would almost certainly yield a lower result if you were having an asthmatic episode. IMV, with the availability now of portable desktop spirometers, there is no excuse for relying so completely on a toilet roll tube and cheap flowmeter for assessing such an important function.

  • hahahah tenorman - love your (surprisingly accurate) description of a PF meter!! :-D

  • I can sound like a zombie blowing drink bubbles with a straw and still get a decent peak flow reading...somehow!

    That about sums up the noise I made taking my peakflow tonight!

  • I found it really interesting (as did curiouser) to blow a PF when well, then quickly reset and without taking another breath do another PF. Curiouser could still get 250 (if i remember correctly) so shows that some people do PF in a way that will generate good results with virtually no air!

  • That's very interesting soph (and an experiment I'll be trying lol) and definately something to bring up with the gp when he tells me that my pf is 'fine' and won't give me pred!

  • Ahh I can't do that sadly - I only get 100-150 (though still, I can actually move it!) Got 320 once but suspect I was accidentally cheating.

    It's good to hear this - several ppl who should be in the know (my GP, a resp nurse doing a lit review on PF as a measure for her CPD) were saying it's really not reliable and I should go on symptoms.

    However, just to confuse the issue, my cons, who I would think would be even more in the know, is very hot on PF and as far as I can tell - and I may be misreading this - has told me I don't need to worry about doing anything if PF is above 300. Very confusing hearing diff things.

    Problem is, PF for me is not that sensitive day to day. It can reflect general trends, but if I'm struggling it may not drop - and I ended up in hospital with not too bad PFs because it was an effort to speak and OOH sent me up there (not a bad attack but an attack nonetheless and they didn't tell me to go away because PF was too high - I wasn't moving much air apparently).

  • It appears that I'm unusual in that there is only really one nurse at my surgery (who is not the asthma nurse really and I only see if I need a quick appointment) who goes off pf. The GP and nurse I usually see are more interested in symptoms. Saying that, I find that pf is usually quite a reliable indication of how I am feeling, especially when looking at the difference between am and pm readings and also after taking meds. Unfortunately for me, they are much more of the looking for wheeze type (which I rarely have). My cons does recognise that my personal best should be much higher than it is and above the normal for my age (apparently this was indicated in my spiro results). I have just tried the experiment Soph tried and I barely moved it (not even hitting 50).

  • I am gathering that PF shows general trends for some and for others its just useless. I feel like I am going to have a good argument on my hands next time a doc tries to send me away because my PF looks just fine

    I did what soph mentioned and got around 350 first time (never been higher than 380) and 240 second time. I think you and curiouser are onto something here! As Philomena mentioned it should only be used in conjuction with other things. I really do not understand why doctors treat it like such a good judge of how your asthma is at that time if there are so many of us arguing against it????

  • OK so just tried, I get 420 and straight after got 290, its not close to my pb of 570, but not bad to say there was no air left in my lungs!!

    Like philomela, pf can show a general trend so when I'm feeling rubbish for a while, my pf results are lower than my pb, however I can feel fine and have a low pf yet another time feel rubbish and have a good pf. Pf is always better at the gps too.

    I work with doctors, I am the technician for a piece of equipment, and with that the doctors know what a positive result looks like and what a negative result looks like, but they can't interpret resukts in the 'grey area', and 'normal' is below a certain value, however some people can be abnormal below this value but the docots struggle with this (hence why I interpret the results and tell the doctor!) So I can see why they struggle with peak flow anomalies, it doesn't make it acceptable though.

  • When doing pf the aim is to exhale as fast as you can until empty. So I would guess that there is a technique issue if you can blow another one without inspiring (ie you are stopping blowing before fully expiring). I blow 300 then 0 ie no air comes out as I've already blown until I can no more.

  • Curiouser: PF is an instantaneous measure of volumetric flow rate - the speed at which a unit volume of air moves. Would not that make it proportional to *force*, not *volume*? Provided one is forcing air through a narrow enough tube/opening in the vocal folds one can generate a great deal of speed with very little total air expelled. Even FEV1 which appears to be a measure of volume isn't really: it is the average flow rate over the course of one second. As long as one has enough air to sustain an exhale for 1 second, the total air in the lungs isn't even relevant.

    Tenorman: even FEV1 can reflect effort and skill: consider a singer who holds out long very even legato scales vs. one who cannot. My FEV1 personal best is about 125% of predicted and I'm guessing it might have something to do with (a) my viewing a high spirometry score as an achievement (b) hours and hours of practice doing very slow two octave legato scales to learn how to keep obstruction from making my air flow uneven whilst singing.

    But one can't very well go around all day breathing like one is preparing to singing oratorios or arias. It would be exhausting. Neither PF nor FEV1 fully reflect the effort of breathing, and according to my pulmonologist the essence of asthma is breathing that is more effort than it should be. PF and FEV1 only show the end result of that effort: ""skill + effort - resistance"". It is a reasonable measure of how well one is compensating for whatever is going on in the lungs. Obviously, if it is very low and one is symptomatic, then one most likely is not compensating well. On the other hand, one can have a high PF/FEV1/O2 saturation and be symptomatic if one is in fact compensating well for the problems. In this case treatment is more a quality of life issue: well compensated or not, it still takes effort and because of that affects quality of life.

    As for a low peak flow without symptoms? This puzzles me, but I think it might have something to do with accommodation. The body finds way to work around breathing limitations as long as they develop slowly enough. How could it be otherwise? Nursefurby's 11% of predicted that she lives with day in and day out would put most of us in resus if it came on suddenly.

    Nurse Furby: maybe not a technique problem: just impatience? Peak flow only detects the maximum volumetric flow rate, which is normally within the half second of a forced exhale. A typical full exhale as one would do for spirometry can last 6 seconds or more but the flow rate will be much less after the first second so it isn't relevant for measuring *peak* flow.

    A second explanation is dynamic/partially air trapping, i.e. air that can be pushed out but only when there is sufficient force: at the end of a forced exhale the diaphragm is in a lousy position to generate much force so it won't push out air that is stuck behind too narrow/too clogged an airway. However, if one forces out all the air that one can and then rests and repositions the diaphragm one is in a better position to force out the remaining semi-trapped air.

    As for me: if I do a forced exhale, reposition the diaphram and do a second forced exhale without breathing in (all with a pinched nose so I don't accidentally passively inhale through the nose): 420 for the first exhale, 100 for the second. Repeat: 400 first exhale, 170 second exhale. Body plesmography and daily observation indicate that I have a tendency to trap air so those results would be consistent with my second explanation.

  • As for a low peak flow without symptoms? This puzzles me, but I think it might have something to do with accommodation. The body finds way to work around breathing limitations as long as they develop slowly enough. How could it be otherwise? Nursefurby's 11% of predicted that she lives with day in and day out would put most of us in resus if it came on suddenly.

    lol thats very true - the human body has a MASSIVE ability to compensate if things develop chronically - whether thats my 11%, or any other illness which would cause greater difficulties as an acute thing. The difficulty I have, is that I am always living on the edge of tipping over into rapid decompensation as I have no reserves, Im already compensating as much as my body is able.

    Reminds me of when I had renal stones - OMG it was indescribable, and they were only small - blue lights and several days hospitalised. My stepfather had a massive staghorn renal calculi with no symptoms at all, as it had grown so slowly and been such a chronic thing that his kidney compensated. He didn't even know he had it until it was randomly picked up!

    Nurse Furby: maybe not a technique problem: just impatience? Peak flow only detects the maximum volumetric flow rate, which is normally within the half second of a forced exhale. A typical full exhale as one would do for spirometry can last 6 seconds or more but the flow rate will be much less after the first second so it isn't relevant for measuring *peak* flow.

    I cant imagine a six second forced exhale.. mines more like two! I agree completely that its that initial forced bit that is relevant to the measurement, but also wonder if the technique is such that much of the air in the lungs isn't exhaled, then it is likely to affect the result.

    Peak flow is of very limited use to me. At 300 (my maximum) Im breathless but coping, at 260 Im hospitalised. Yet on occasions at 300 I can barely string a sentence together or move. I eventually asked about this at one of my appointments, and was told by Consultant that its of less use in small airways disease and PF is a more accurate measure of larger airways functioning (bronchi) which is what most asthma patients have difficulties with when they narrow in an exacerbation. (Rather than the bronchioles and alveoli).

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