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Spirometery - a little confused

Hi, I'm currently captured (hopefully only until tomorrow) and not too bad actually! Between the 3 times I've done spiro (I'm brittle and have only started doing it regularly since changing to a specialist centre) there's been an overall variation of 19%. Between the last time the variation was 6%

All of them have been done at the end of an exacerbation, so no idea what my Spirometery is doing the rest of the time! I just wonders what this means with regard to asthma and variation etc? I'm a little confused!

Still not allowed out today, gonna be tomorrow at the earliest. Eventhough I'm fine!

Any ideas? xx

4 Replies

Nooooo Laurs Huggs I really hope escape tomorrow!

Do you mean variation in FEV1? My FEV1 varies hugely when I first started doing spiro regularly I was sitting with an FEV1 of around 0.93L and the other week I managed a whole 2..17L so a variance of 43%. You would expect spiro to vary dependant on how your lungs are at the time.

Also the variation is very typically asthma, that's what our lungs do we know one minute we can feel grand the next we fighting for breath!

I hope you feel a bit better and that the specialist centre is starting to get things under control for you, goodness knows you deserve a break.

Becca Xx


My spiro varies hugely - for the last month my pulmonologist has been taking weekly spiro measurements. I've gotten everything from 54-97% personal best (69%-120% predicted) in just 5 weeks.

My variation is huge, but even 19% difference between sessions is higher than normal. I believe 10% variation in FEV1 between visits is considered a significant change (ATS/ERS 2005 joint statement on spirometry - see ).


Just to check, is variation calculated as (higher-lower)/higher? And calculated on percentages or absolute figures?

Because this thread has just made me realise in that case, I have a fair amount of variation too and hadn't realised that this meant anything. My cons never comments on spiro and when I have asked just said it wasn't good quality. Admittedly I do seem to struggle with doing it at times and maybe that explains some of it but on the other hand I asked the clinic nurse once (a lovely one who seems to know me and my numbers etc quite well now) and she said I was doing it ok and the number just wasn't great. And when I was feeling better after starting Phyllocontin (turns out was sub-therapeutic and no-one told me for 2 months grrr but was still helping a bit) it was definitely higher.

I also find it does broadly correlate with how I feel - I got about 60% of personal best FEV1 once (68% predicted), was already struggling and ended up with ambo/A&E later. I saw a diff cons that time and he did comment on it -sort of assuming that meant he thought it was a valid result as he was on about the number etc not the technique. I said realised it wasn't that low but not my best and also that PB was a bit higher than predicted and I usually did better; he basically agreed but didn't say more.


I don't think there is any consensus on how to measure variation - a number of research articles comment on this.

For pf monitoring:

max-min/max is used in BTS-SIGN standards for brittle asthma

max-min/mean is used in a number of research papers

max-min/min is sometimes used as well.

In other contexts:

post-pre bronchodialator/pre bronchodialator is used in commonly used in bronchodialator tests

current visit-previous visit/ previous visit is sometimes used to measure between visit variation.


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