Asthma: What does Peak Flow really mean?

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  • Asthma: What does Peak Flow really mean?
  • surfer
    Member

    I’ve been asthmatic since I was a baby.

    I found that as I got fitter, the symptoms reduced and I nearly forgot that I had it (except when in dusty rooms, near cats or using feather pillows).

    +1

    I have done them for years and seen it as a challenge to blow it to the top. Very hard to now but put it down to old age (47) Suspect your GP sees that result as very good given the “ill” people he sees. Thats why hes a bit vague probably

    FunkyDunc
    Member

    There a charts that show that Peak Flow decreases with age, but there is a range of flow for a given age.

    Obviously at your age your avg should be 650 but your below avg.

    I’ve recoverig from Pneuomonia and my Peak Flow was down to about 250 at one point (when I could actually even do it), I havent taken it recently so will try again tonight.

    Peak flow though should be used to show if Asthma is under control

    Read more here…http://www.peakflow.com/top_nav/home/index-2.html

    “Peak flow meters play an important role in the management of asthma for a large number of patients, by indicating the how narrow or open the airways are. Peak flow readings are higher when patients are well, and lower when the airways are constricted.”

    Mrs FD was explaining a lot of it to me when I had Pneumonia, hence I have forgotten it, but basically I think the basis is you have a capacity, but then things happen to reduce that capacity ie illness. I’m not sure about the training to improve it bit though

    surfer
    Member

    Theres also a technique. Its not “blowing” as such its a very sharp exhalation, ask him can you have a few tries.

    the teaboy
    Member

    Suspect your GP sees that result as very good given the “ill” people he sees

    Hadn’t thought of that. Good point.

    I should have bigged up the fitness thing, though he got a hint after I turned up looking like a drowned rat, having ridden there through an epic downpour.

    Premier Icon molgrips
    Subscriber

    I know someone who couldn’t beat 100 on those little tube things.

    the teaboy
    Member

    Peak flow though should be used to show if Asthma is under control

    This is the bit I get – it’s about providing a baseline from which deviations become meaningful.

    What I don’t get is what it actually means in terms of an impact on daily life.

    Surfer (^ up there) can blow it off the scale. I can’t. Does it mean that his lungs help him ride faster or is it just that he can blow into a tube better?

    Premier Icon GrahamS
    Subscriber

    Theres also a technique. Its not “blowing” as such its a very sharp exhalation

    I did this. Blowing sharply like a theatrical “Tut”, as you might to clear a snorkel while diving.

    I can easily hit the end of the scale doing that, but apparently “That’s cheating”

    Blowing “normally” I’m usually around 600.

    Premier Icon scaredypants
    Subscriber

    It’s just a measure of how “open” your airways are – you can squirt air faster down a wide tube than a narrower one. It’s harder to breathe out than in when yr airways are v narrow which is why he’s talking about expiratory airflow

    Individuals vary, and practise on the devices makes a difference too

    540 ain’t bad and probably isn’t limiting your performance (I’d GUESS) but really needs to be seen against your normal figure – docs get very interested as you approach 50% of what you can normally manage during a wheezy episode

    don simon
    Member

    I’ve heard stories of asthmatics having a crafty fag before doing the test just to get the numbers up. 😯
    My doc was more interested in the difference between morning tests and evening tests.

    the teaboy
    Member

    really needs to be seen against your normal figure

    I’d guess that this is my normal figure – I feel fine and have no symptoms.

    So all it means is that I have to work harder to breathe out?

    FunkyDunc
    Member

    For fitness though isnt it kind of irrelevant because you are where you are?

    Wouldnt you need to do one of those treadmill test things to properly compare 2 peoples fitness?

    surfer
    Member

    Does it mean that his lungs help him ride faster or is it just that he can blow into a tube better?

    Possibly both. I’m an asthamtic and suffered a lot as a youngster and teenager. Took up running at about 19 and ran a lot since then competitively (not the same as fast!) and I think thats helped a lot but as above maybe my technique is good, although it was how I was told to do it.

    surfer
    Member

    Wouldnt you need to do one of those treadmill test things to properly compare 2 peoples fitness?

    Vo2 max tests are a different thing. I had one done when I was at Uni. I apparently had a similar reading to John Tracey! I think other factors make you a good long distance runner, not just Vo2!!!

    the teaboy
    Member

    Might be irrelevant in that I can’t do anything about it but I hate not knowing things!

    rogerthecat
    Member

    Mrs Cat is a sufferer and we have had some “interesting” rides in various emergency vehicles after failing to hit the desired flow.

    As has been said, its mainly about how efficiently you can evacuate spent air from your lungs and suck in more oxygen rich air.

    Lower flow = lower exchange of air = lower blood oxygen saturation all of which will have an effect on your performance.

    In Mrs Cat’s case it limits her riding to flat trails/converted railways etc (that and having a sizeable quantity of high tech scaffolding in her spine), I used to ride with a guy who was not quite as bad and his answer was to pump himself full of various inhalers and drugs and damn the consequences.

    Fitness will really help, breathing control is also important but you will hit a ceiling.

    FunkyDunc
    Member

    ” I used to ride with a guy who was not quite as bad and his answer was to pump himself full of various inhalers and drugs “

    Other than the inhalers prescribed by a GP?

    the teaboy
    Member

    I’ve been asthmatic since I was a baby.

    I found that as I got fitter, the symptoms reduced and I nearly forgot that I had it (except when in dusty rooms, near cats or using feather pillows).

    I went to the docs today and he asked me to do a Peak Flow reading. The line said I should have been hitting 650, but I could only do 540.

    He gave me the usual chat about airflow when breathing out but was very light on meaningful detail, so here’s where you lot come in:

    What does a low Peak Flow mean in terms of fitness and my ability to ride and run?
    What benefits am I missing out on from having a low Peak Flow?
    How much quicker could I run if I had normal lungs?!
    Is there any way to train my Peak Flow?

    Premier Icon Kona TC
    Subscriber

    As an Asthma suffer since I was a small child and now the other side of 50 my peak flow for the last 10+ has declined from an average of 480 (morning and afternoon combined) to 450.

    I have seen the chart posted by FunkyDunc before and questioned my doctors/asthma nurse on its validity and like most ‘medical’ charts/tables its open to interpretation.

    So I have settled on a combination of drugs (medication) and monitor my peak flow first thing each morning and early evening, tracking the trend. I only take action when I feel of see a change in my reading. My view for what its worth is the ‘peak flow figure’ should only be used to track your norm.

    If you feel well, your asthma is not impacting on your normal activity level then life is good

    the teaboy
    Member

    Lower flow = lower exchange of air = lower blood oxygen saturation all of which will have an effect on your performance.

    This makes sense. I wonder whether if I train constricted and race with Salbutamol I’ll be more efficient…

    your asthma is not impacting on your normal activity level then life is good

    Absolutely. I’m lucky that it doesn’t affect me much. Lots of people are much worse off (sounds like FunkyDunk has had a rough time).

    As above, I hate failing to understand things about my physiology!

    Premier Icon martinhutch
    Subscriber

    I’ve been an asthmatic since childhood, quite severe and uncontrolled for most of it.

    Now I’m better controlled, 500 is about par for me.

    One thing I noticed about managing to improve my peak flow over time is that the onset of noticeable muscle fatigue during aerobic exercise was definitely earlier when my peak flow was at a lower level – this was independent of actual asthmatic symptoms at the time and overall underlying fitness levels as far as I could tell. Presumably because even subtle changes in O2 transfer have effects on lactic acid dispersal when you’re working hard.

    But I personally don’t obsess about peak flow except when I have a respiratory infection, which I haven’t had for some time. I don’t think that denying yourself salbutamol during training will necessarily improve your metabolism of oxygen etc. In my mind you should concentrate on getting the dose of your preventer spot on so that salbutamol becomes almost totally unnecessary at any time, and not deny yourself the reliever if you have symptoms.

    Premier Icon Trekster
    Subscriber

    Had peak flow measured yesterday at docs and just managed 600 using the standard pf meter.
    At work an electronic device is used giving a number of different readings, one of which is elasticity. All my age related readings except the elasticity one is above average. The elasticity one is only 75% which means oxygenation of blood is poor. Think I have got that correct 🙄

    Teaboy,I had about the same result as you recently at the docs.He indicated it was a very good result.Not exactly great weather for an asthma sufferer either.

    Poopsies
    Member

    Slightly bizzarely I’ve just googled “peak flow only 540” and the first hit I got was this thread on Singletrack. I had a company medical today and got 540. I looked at the chart FunkyDunc posted above online earlier and I’m way off where I should be as a 40yo. I’ve always been fit – used to be able to hold my breath for 2 1/2 mins, ran the 400m for an athletics club, played all sorts of sports and have never felt that the limiting factor to my fitness was an inability to suck air and and out and I’d definitely say I have always been fitter and faster than most of my mates. Never had asthma as far as I know although I did used to smoke.

    It’s no big deal I suppose but I am wondering if there is anything I can change. My wife says I should stop obsessing!

    Nonsense
    Member

    It’s very technique based as well. I’ve had asthma since I was 2 and been hospitalised with it when I was younger. My lung function is actually very good when I don’t have a cold or chest infection and I usually hit between 680/700 on a peak flow. But if you don’t know the technique you’ll never hit your max. You can buy one from the chemist or borrow one from the doc to keep an eye on your measurements over a week or so.

    matther01
    Member

    I was reliably informed that most people breathe incorrectly as they move from childhood into adulthood. This may sound daft, but try sucking air into your tummy, so that your tiny sticks out and then gradually fill up your lungs instead of just filling up your lungs and puffing up your chest. I’m really unfit but did this for my test and scored higher than someone who plays a trombone!

    DrP
    Member

    As has been said, its mainly about how efficiently you can evacuate spent air from your lungs and suck in more oxygen rich air.

    Lower flow = lower exchange of air = lower blood oxygen saturation all of which will have an effect on your performance.

    This is kind of true, but only in extremes of asthma attacks.
    If you have a slightly reduced peak flow, you’ll have normal SaO2 (sats) levels.

    What is peak flow….
    It’s a measurement of the maximum ‘speed’ you can exhale air at.
    It doesn’t measure how much air you blow out (this is lung capacity, which can be measured on a different machine), but…obviously if you have tiny lungs, you’ll blow out less air, which will ‘move’ the peak flow ‘spring’ less (which is why peak flow charts are based on height/sex.)
    Peak flow can be reduced by airway obstruction (purse your lips and try and blow out forcefully – the air comes out at a piffy rate doesn’t it – this is just a ‘narrowing’ at the lips, but in asthma ths narrowing occurs ‘inside the lungs’ but has the same effect. Try breathing hard for 1 minute through pursed lips – not nice is it…!)
    However, peak flow can also be reduced by ‘illness causing reduced lung capacity’, and poor peak flow technique.

    Spirometry is the ‘gold standard’ test as it compares FEV1 (forced expiratory volume in 1 second – how much air you can blow out in one second) against your FVC (forced vital capacity – how much air in total you can blow out to completely empty your lungs). It’s the comparisons that’s useful, but of course this is a fancy and time consuming test, and in the majority of cases, peak flow is great as it compares yourself against yourself…!!

    Essentially, a low peak flow (i.e. poorly controlled asthma) will make sport and activity harder)

    DrP

    Premier Icon Doh1Nut
    Subscriber

    I think peak flow is best considered like weighing yourself on a cheap set of scales, you know the number wont be correct but if you keep everything else constant then if the numbers go up and down then they mean something.

    I guess I have a “good” technique as the last result at the doctors was 780 which was a nice surprise but my ride to work this morning was a painfully plodding 13.4mph that probably better reflects my fitness level.

    hammerite
    Member

    It shouldn’t really be about technique, it is what it is. I can score highly if I “spit” my breath hard into the tube – but like someone says above it’s cheating (I got told off when I tried that). If I blow hard then the score is significantly less. I usually only make around 450.

    Last time I had one of these I asked the doctor if it demonstrated anything about my fitness, compared to my peers (bearing in mind I’m probably a lot fitter than the vast majority of the public). His answer was no, comparing scores with someone else is pretty much pointless. Where it helps is to monitor where you are at the particular time (and how well/ill/healthy you may be) – when compared to scores on other occasions when you’ve taken the test.

    Premier Icon Trekster
    Subscriber

    Long term sufferer. “Normal” pf is around the 600 mark on a pf meter.
    At work I get a yearly teats which is done on a a machine which is possibly what DrP describes. I have had a few chest infections over the past few winters and on my recent test I have lost 6% on the function which does the blood oxygenation bit, down to 75% 🙄 Every other function is above 100%. This would appear to coincide with me getting slower and struggling to climb hills on the bike 😉 That and putting on half a stone 😕
    Being an auld bloke most nurses are surprised at my readings but I have always been active whether it be biking, running, swimming, squash or badminton

    hammerite
    Member

    My Dad has been a postman for years, they used to give medicals to everyone when applying for a job (not sure if they still do). He failed the medical as he was unfit, based purely on his very low peak flow score. He questioned this, as he’d just completed a marathon in bang on 3hrs.

    Had to prove he had completed the marathon in that time, and then he got the job.

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