electric peak flow meters

Hi, I know a few of you use electronic meters, but wondered if any of you had similar strange readings.

I've had and used my Asma-1 for two months, but on occasion (3 times last week) and several times before over the two months, but this morning for example the peak reading was 661, while the other 2 readings were 561 and 562. Bit lower than I would expect, but the 661 is on the high side, as the usual readings at the moment have been around 580-600.

I'd always ignored these high readings, as I thought they were errors, but not so sure after having 3 similar high readings on 3 seperate days last week, but the other 2 puffs out of the 3 were back at the lower level. If the high readings are accurate then this would put my personal best at 688, and not 626 as i'm using at present, meaning that my condition is managed at the lower end of acceptable and not near the top as I'd thought based on personal best.

Any suggestions or comments.


18 Replies

  • i didnt even know there was such a thing as an electric peak flow, have you tried doing your peak flow measurements on a non electric one for a while to see if you are getting the same scores?

  • hi plumie,

    thanks for the suggestion. yes I did try that, but have never managed to get the manual version above 560, which I don't think is actually accurate, as when I bought the electronic version I did try both and got similar readings over the two days I used both. Since buying the electronic one, I have got better, but the manual one still give the same low reading.

    this is the electronic version I have



  • My peak flow varies by about 50 from my piko 1 meter to normal PF meter. I don't trust my piko 1 for PF only really use it for fev1.

    If your original PB was measured using normal PF meter I wouldnt worry as with my experience the elctronic ones do vary and tend to give a higher reading.

    Hope this helps


  • Hi Woody, try recording FEV1 readings as well to see if there are high FEV1 measurements corresponding to the high peak flows.

    FEV1 is the forced expiratory volume in one second - the volume of air that you can blow out in a second measured in litres (L), and can also be used to monitor asthma. Sometimes I find that FEV1 is usually fairly steady over three readings, but peak flow can vary slightly.

    It's fine to use the manual meter - readings can vary between meters of the same make and model, but each meter produces consistent readings with itself. What really matters then is the percentage difference between readings using the same meter.

  • hi clare22

    Not really good enough is that for something that should be more accurate, considering they cost 3 times the manual version.

    My PB was set using the electronic one, if I still used the manual I'd be getting results of 550 all the time at best, but I know thats not accurate as I can feel air escaping from the joins, and that was from new. According to the data tables I should be around the 650 mark, but the a doctor who I cycle with says that all the cycling, swimming and running i do should put me nearer the 800 mark.

    How do you find the FEV readings. I'm not sure what it should be or how much variation is acceptable, but have recorded this, and tend to be more stable than PEF readings.

  • Hi Ginny

    I do record the FEV figure, and that is reasonably stable, but a high FEV doesn't always mean a high PEF, actually the opposite. Anyway, I phoned vitalograph to ask advice, and all were in a meeting, so someone is going to return my call tomorrow, hopefully they can clarify this.

  • i know i dont use an electric one, but i personally find when using a normal one, that my first blow is always higher and my next two are lower. Probabley becuase doing peak flow makes me cough or breathless. So your first one being high could be a true reading, and the next two lower as you are more tireder. if that makes any sense?

  • Woody-som where you experiencing more symptoms on these other days? I dont rely solely on my PF as I run quite low so I mainly go by symptoms.

  • Hi Chris, there are tables giving predicted FEV1 measurements based on sex, age, height and ethnicity. But it does vary between individuals in a similar manner to peak flow. I *think* that one can compare readings using a personal best FEV1. Will try and see if I can find a table of predicted values online!

  • Heres a spirometry calculator so if you already know your recent FEV1 it will then give you your predicted. I f you dont know your FVC just type in any number bigger than your FEV1.


  • plumie, yes my 1st is usually the highest, but 100 l/min on the same reading set and 60 l/min above what I was expecting is I feel wrong, the others last week and the few over the preceeding weeks were similar, and I did ignore them to start with. If like you say the 1st is correct, then I need to have my meds reassessed as the other readings put me usually at 81% of best +/- 2%.

    Clare, PF is the only way I can monitor things really, I get symptoms when I'm really bad, I've felt no worse or better over the last month, so can't really say that has influenced the readings.

    Ginny, tables would be good, I did find a list to formula to calculate the FEV, but all 8 of them gave slightly different results with a range of lowest normal 3.2 to a max high of 4.4. The newer ones (1991 and 1983) gave similar results so could assume 4.39 as near enough, which would mean over the last month my FEV average is 87% of predicted - strangely the PEF of 562 this morning is also 87% of my predicted 647.

  • Hi Chris, there doesn't appear to be much in the way of tables online. Did find a spirometry calculator at


    where you put in values for age, sex, height, FEV1, and FVC to generate predicted readings. I found it was okay to enter a random slightly higher figure for FVC to get the 'Calculate' button working.

    *Edit* Sorry Clare, just realised we've posted the same link!

  • thanks for the links, this is the formula Iist i found pick the formula that takes account of ethnicity, as well as sex.

    predicted FEV1 in liters for males (Boren, 1966) =

    = (0.094 * (height in inches)) - (0.028 * (age in years)) - 1.59 =

    FEV1 in liters for White males 15-79 years (Cherniack, 1972) =

    = (0.09107 * (height in inches)) - (0.0232 * (age in years)) - 1.50723

    FEV1 in liters for White females 15-79 years (Cherniack, 1972) =

    = (0.06029 * (height in inches)) - (0.01936 * (age in years)) - 0.18693

    FEV1 in liters for Hispanic males 25-80 years (Coultas, 1988) =

    = (3.7708 * (height in meters)) - (0.0288 * (age in years)) - 1.6205

    FEV1 in liters for Hispanic females 25-80 years (Coultas, 1988) =

    = (3.2138 * (height in meters)) - (0.0243 * (age in years)) - 1.4184

    FEV1 in liters for White males 15-91 years (Crapo, 1981) =

    = (0.0414 * (height in cm)) - (0.0244 * (age in years)) - 2.190

    FEV1 in liters White females 15-84 years (Crapo, 1981) =

    = (0.0342 * (height in cm)) - (0.0255 * (age in years)) - 1.578

    FEV1 in liters for Hispanic males 25-75 years (Crapo, 1990) =

    = (0.0451 * (height in cm)) - (0.0301 * (age in years)) - 2.7721

    FEV1 in liters Hispanic females 20-80 years (Crapo, 1990) =

    = (0.0378 * (height in cm)) - (0.0189 * (age in years)) - (0.0048 * (weight in kilograms)) - 2.1371

    FEV1 in liters for Chinese males 20-66 years (Da Costa, 1971) =

    = (0.0267 * (height in cm)) - (0.0189 * (age in years)) - 0.774

    FEV1 in liters for Chinese females 20-66 years (Da Costa, 1971) =

    = (0.017 * (height in cm)) - (0.0175 * (age in years))+ 0.232

    FEV1 in liters for White males 65-85 years (Enright, 1993) =

    = (0.0378 * (height in cm)) - (0.0271 * (age in years)) - 1.73

    FEV1 in liters for White females 65-85 years (Enright, 1993) =

    = (0.0281 * (height in cm)) - (0.0325 * (age in years)) - 0.09

    FEV1 in liters in adult males 20 - 65 years of age (Grimby, 1963) =

    = (3.44 * (height in meters)) - (0.033* (age in years)) - 1.00

    FEV1 in liters in adult females 18 - 72 years of age (Grimby, 1963)

    = (2.67 * (height in meters)) - (0.028* (age in years)) - 0.54

    FEV1 in liters for White males 25-85 years (Knudson, 1983) =

    = (0.0665 * (height in cm)) - (0.0292 * (age in years)) - 6.5147

    FEV1 in liters for White females 20-88 years (Knudson, 1983) =

    = (0.0309 * (height in cm)) - (0.0201 * (age in years)) - 1.405

    FEV1 in liters for males 18-66 years (Kory, 1961) =

    = (0.037 * (height in cm)) - (0.028 * (age in years)) - 1.59

    FEV1 in liters for White males 20-84 years (Morris, 1971) =

    = (0.092 * (height in inches)) - (0.032 * (age in years)) - 1.26

    FEV1 in liters for White females 20-84 years (Morris, 1971) =

    = (0.089 * (height in inches)) - (0.025 * (age in years)) - 1.932

    FEV1 in liters for Black males 15-74 years years (Mustafa, 1977) =

    = (0.046 * (height in cm) - (0.022 * (age in years)) - 3.864

    FEV1 in liters for White males 18-86 years years (Roberts, 1991) =

    = (3.961 * (height in meters)) - (0.033* (age in years)) - 1.558

    FEV1 in liters for White females 18-86 years (Roberts, 1991) =

    = (3.321 * (height in meters)) - (0.025* (age in years)) - 1.394

    FEV1 in liters for Black males 20-92 years years (Stinson, 1981) =

    = (0.096 * (height in inches)) - (0.021 * (age in years)) - 2.51

    FEV1 in liters for Black females 20-92 years (Stinson, 1981) =

    = (0.062 * (height in inches)) - (0.017 * (age in years)) - 0.951


    • The FEV1 reflects the severity of pulmonary impairment in obstruction.



    > 80% predicted


    66-80% predicted

    mild obstruction

    50-65% predicted

    moderate obstruction

    < 50% predicted

    severe obstruction

    just found this one if U scroll down the page, will calculate FVC as well brianmac.co.uk/spirometer.htm

  • Hi Chris, it seems that peak flow measurements should be repeated until the highest two are within 40 l/min.

    From page iv17 of the 2008 BTS Guideline on the Management of Asthma


    (points to



    PEF should be recorded as the best of three forced expiratory blows from total lung capacity with a maximum pause of two seconds before blowing. [88] The patient can be standing or sitting. Further blows should be done if the largest two PEF are not within 40 l/min. [88]

    PEF is best used to provide an estimate of variability of airfl ow from multiple measurements made over at least two weeks. Increased variability may be evident from twice daily readings. More frequent readings will result in a better estimate [89] but the improved precision is likely to be achieved at the expense of reduced patient compliance.[90]

  • ginny, that doc makes interesting reading. don't think if i stayed all day trying that i'd get within 40 l/min of the high readings again. The others however are usually well inside that range.

  • UPDATE - Sales rep phoned today and I explained the situation to him, and he said that it sounds like the device is giving erratic readings and should send it back for a swap, but he couldn't explain why a 15% variation in a same set reading. anyway, i'll have to give vitalograph a ring in the morning to put that in motion.

  • That sounds promising Chris. I have more reading for you :) - a link to FEV1 tables on the National Asthma Council Australia Website:


    which points to


    You also mentioned that air escapes from the joins of your other peak flow meter. When blowing into my Mini-Wright, air only escapes from the groove that the red slider rides in, and the end. Can't feel anything around the red bit joining the mouthpiece to the light grey plastic. But suppose it's best to sort that out after the Vitalograph comes back - one thing at time :).

  • bought a piko the other day-waiting for it to arrive now! Figured it was a good idea to monitor peak flow and fev1 as this will give me and my gp/consultant a better idea of what is happening with my asthma over a day and over time! Anyone got any suggestions for how often they measure pf and fev1 at the moment i measure my peak flow 2 times a day first thing and just before bed and when im unwell as i am at the moment i was told to measure it 4 times a day before and after the ventolin and atrovent nebs! This then gives my gp/consultant an idea of how my peak flow changes after the nebs! Anyone else do anything different? I find it very time consuming and also find i wheeze quite a lot after doing the peak flow- it also makes me cough an awful lot as its the same sort of technique that i use with the physio to clear mucus off my chest-the huffing technique!! Mmm think peak flows are bad for me lol!!!

    Any advice on the piko is very much appreciated-bought it as i thought it would be helpful to know what my fev1 is so that i could have a rough idea of numbers aswell as symptoms to better evaluate when i needed to go into hospital as i seem to be spending far far too much time in there at present and will do anything to avoid it if thats at all possible! Sure there are a lot of other people out there who share that feeling tho!!

    Thanks in advance for the advice and help peeps- feel free to pm me if you dont want to post publically any info will help! Ta everyone! Lv cupcake Xx

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