Asthma UK community forum

New and wondering about peak flow's


I've recently joined AUK in an attempt to stop being 'head in the sand' about my asthma! There's loads of really usefull info and everyone seems friendly, I'm just a bit confused by peak flows.

My asthma's been playing up since about October last year - with repeated chest infections and generally being really annoying. So my asthma nurse is being really firm with me (a good thing) and getting me to track my peak flow am and pm (I've never really done this before) as I'm not good at noticing small/moderate changes and then it's hard to get control back once I've gone from ok-ish to bad.

So my questions are - in someone with well controlled asthma what difference would you expect between am and pm readings? Or should they be about the same? My am readings seem to be a lot lower than the pm ones (280-310 vs. 400-420, with all time best of 450)- which makes sense (I think) as the over night/early hours patch is not great but once I've got over the night the days in general are now much better. This really confuses me about when and how often to increase my dose of symbicort!!

I will check at my next review but any ideas or tips would be great!

Thank you!

4 Replies

My am readings are always lower than my pm ones (and I think that's the expected pattern), but I don't think they should be as extreme as yours (my asthma is currently *crosses fingers* quite well controlled and I have a difference of about 10 - 40 with a best of 505). However, by keeping a record, you will be able to share this with your asthma nurse and they will be able to advise.


diurnal variation as it's known is a good guide to how well your asthma is controlled.

Diurnal Variation

This is the difference between the width of the airways in the morning and evening on one day measured about 12 hours apart. The airways are narrower at different times over 24 hours even in people who do not have asthma. Research has shown them to be widest at 4pm and narrowest at 4am. In people with asthma, this difference is exaggerated. Instead of varying by about 10%, they vary by 20% or more. This is a sign that asthma is present and unstable: that is, the airways are twitchy and irritable.

Morning Dip

It is not uncommon for peak flow readings in the morning to be markedly lower than the evening in people with asthma. This is often referred to as the morning dip. The exact reason why this happen is unknown. There are many ideas as to why it may occur, including acid leaking from the gullet at night, posture during sleep, low levels of body steroids at night and other theories, but it still remains a mystery! A pronounced morning dip i.e. in your yellow zone or less, indicates poor or worsening asthma control. If you have a morning dip but your evening peak flow remains high, then it follows that your diurnal variation will go up.

I find the mornings to be lower but not always, somedays the evening reading can be lower, but as long as it's within a range that I have got to know is OK i don't tend to worry.

i use a free computer program to record the peak flow readings, and it works out the percentages, and produces nice graphs that help me understand how things are working. google asthma assistant.


Thanks for the info guys! :)

Really good to know a morning dip is quite common and hopefully I'll get to know my own patterns over time. Will definitely google that peice of software you mentioned Woody-som. After a night that was worse than norm I think I have decided it would just be better if the whole night time thing was an optional extra to life and we could all manage fine without sleep!!! But at least it's Friday :)


Lee, something you may not have read, or know about, as your new here, is that the position you sleep in does have some impact on your night symptoms. It usually better to sleep on your side, and if possible prop yourself up. I actually did one better and put a couple pieces of 4x2 under the two top bed legs, creating a slanting bed. It helped me, and some here use adjustable beds, or sleep more sitting up. Try several methods, and see which works best, but the wood or even a brick is cheap and easy to try.

good luck with the monitoring, it gets easier with time, and you will learn to pick up on patterns. I like the software, because if I notice it shows 8 red downward arrows in a row, I need to be careful, something I never seemed to notice on the little graph, but that ay be just me, bit of a techno geek anyway.



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