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Recording peak flow meter readings

Demonstrate the peak flow graph and calculation for diurnal variation.
This is a graph of peak flow metre readings performed for two weeks. The arrows show the variation between morning and evening readings. The lowest reading was 400 litre per minute. And the highest reading was 500 litre per minute. To calculate diurnal variation, minus the highest rating to the lowest rating and then divide it with the mean of the day’s highest and lowest. Multiply it by 100%. Let me show you the calculation based on the previous graph. 500 minus 400 divided by 450, which is the mean of the day’s highest and lowest, multiplied by 100%. The diurnal variation for the previous graph was 22%. Calculation of more than 20% is suggestive of asthma.

Peak flow variability features in many patients with asthma, and there are many ways to calculate it. Some calculations can be complicated for the clinical setting, e.g. the amplitude percentage mean. We will show you a simple approach for estimating peak flow variability.

This video demonstrates how to record peak flow meter readings and how to calculate the diurnal variation of the readings.

You can also download and use the example PEFR flow meter graph from the Downloads area below.

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