Asthma UK community forum
10,123 members16,763 posts

I have heard that there should be slight decrease in peakflow between morning and night, but no clarification on what that means. So what is a normal difference between PF for morning and night? Do they mean by ten or fifteen or twenty? My PF tends to jump around within the 550-590 range so one day may be 590 Morning and 590 evening. Or it might go 590, 560 or 580, 550.

I know my asthma is not well controlled--I am just trying to get an idea of what is "normal" so that I have something to aim for.

9 Replies

Yes you’re right, peak flow has what is known as diurnal variation, but there’s some evidence to show it can be cyclical over days or longer periods. Although treatment focuses, probably correctly, on your personal best it’s certainly useful to know how it works for you. Morning is generally the point it will be lowest but teaching yourself over time what that means for you will help you I’d imagine.

If you’re handy with Maths there’s a formula here for using measurements to calculate diurnal variability:

ncbi.nlm.nih.gov/pmc/articl...

It’s figure 1 a little down the page.

Ah, Math. My arch-nemesis rears its ugly head once again XD Let me take a look and see if I can figure this out ^_^ Thanks!

I wonder if this can be entered as an excel formula. I enter my peak flow diary into an excel sheet so I can track and plot more items and compare them more easily.

I'm sure it could. I'm OK with Maths & fairly OK with Excel, so I'll see what I can do - no promises though!

Thanks! i can also get my hubby to work on it, too. right now, I am a little under the weather so I can't do much thinking.

I think I’ve nearly cracked it. I’ll test it out this afternoon & let you know. Sorry to hear you’re under the weather anyway. Hope you soon feel better

wow, thanks! i think this will be helpful for many people. I read on the article you linked that it is more accurate to have four times a day testing of PF, but they also mentioned something about an ideal time frame that fluctuates based on when you wake up. Wow. I will have to read it more carefully later.

Hiya - just to let you know I've finished a draft spreadsheet (loads of caveats about possible errors & not relying on it, etc.), but if you want to have a play with it & see if it works for you, let me know where to send it. I'll explain how it works as well, as I've tried to make it user friendly!

wow, you are awesome! I think I can send you my email in a pm, hold on.