Why does my peak flow vary so much?

People get different peak flow scores depending on their age, height, and gender. Peak flow can vary at different times of the day too. For example, it’s normal for your score to be slightly lower in the morning. The most important thing is whether your score is normal for you.

Can a peak flow meter be wrong?

Results: Nine studies have reported errors in performing the PEF maneuver, including three pediatric and six adult studies. Errors were found at most steps of the maneuver, and inability to perform all steps correctly was common in these investigations.

How much peak flow variation is normal?

Peak flow rates are commonly split into three zones. The colors of a traffic light – green, yellow, red – are used to represent the three zones. In general, a normal peak flow rate can vary as much as 20 percent.

Is a peak flow reading of 250 bad?

That’s your “normal range.” Your yellow zone would be between 250 – 400. And your red zone would be anything less than 250.

What is the average peak flow for a 60 year old?

between around 400 and 700 litres per minute
Normal adult peak flow scores range between around 400 and 700 litres per minute, although scores in older women can be lower and still be normal.

How do I know if my flow meter is accurate?

to know the accuracy. The accuracy of a flow meter can be stated one of two ways; as a percentage of full scale (FS) or as a percentage of reading (RD, also referred to as per- centage of rate). It is important to understand the meaning of both so that your flow meter performs as expected and with the desired accuracy.

Are Rotameters accurate?

Even in the most demanding applications — measuring gases, liquids or steam — rotameters can deliver 2\% full-scale accuracy. Rotameters are inexpensive flow-metering devices for a variety of industrial processing applications.

Why do you get diurnal variation in asthma?

Circadian variation in asthmatic shift workers was intimately related to sleep and virtually independent of solar time. Treatment tends to lose its effect as it is discontinued during sleep and this increases the apparent diurnal variation in many patients.

What peak flow reading indicates asthma?

Yellow zone = caution Your peak flow rate is 50\% to 80\% of your personal best, an indication that your asthma is getting worse.

What peak flow indicates asthma?

Green, yellow and red: Understanding your peak flow zones Your peak flow rate is 80\% to 100\% of your personal best, an indication that your asthma is under control.

How do you calibrate a flow meter?

To perform Master meter calibration:

1. Place the master meter in series with the flow meter under test.
2. Compare the readings of the master flow meter and flow meter using a measured volume of liquid.
3. Calibrate the flowmeter under test to conform with the master flow meter calibration.