Peak Flow Varience

My Peak flow in the morning is 430-450 and in the evening its 350-400. What is classed as a uncontrolled varience?

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diurnal variation, the difference between morning and evening basically boils down to 3 ranges

0-10% Excellent

10-20% Acceptable

20-30% Poor

so if you had a reading of 450 in the morning and then 350 in the evening then that is poor as it's more than 20% variation.

the stability of your morning or evening readings is way better than mine. last 4 weeks for me and this is very typical morning 565-685 evening 581-758 (lows are probably a bit lower than normal)

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Woody-Som, what should these percentages be taken of? Best peak flow, morning peak flow or evening peak flow?

Is it more normal to have higher morning or evening peak flows? Mine have always been higher in the evening.

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Diurnal Variation 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.

The figures you should use to calculate your diurnal variation are the readings you acheive on the day, and not predictions or personal bests.

Morning Dip 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.

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Thanks for the info. My PFs hardly ever get out of the yellow zone. Mm.. peak flow maths. Something for me to while away the small hours on when I can't sleep.