# Peak Expiratory Flow Measurement

## Overview

This module describes how to use peak expiratory flow measurement in asthma and COPD.

## Indications

1. Severity grading of acute exacerbations of asthma or COPD

2. Monitoring severity and control in chronic persistent asthma or COPD

3. Differentiating COPD from asthma by measuring reversibility

## Contraindications

1. Patients younger than 5 years of age

## Patient information & consent

Always verify your patient’s identity and obtain informed consent before proceeding.

### How do I explain this procedure?

“We need to measure how well your lungs are working. When your asthma is poorly controlled, the amount of air you can breathe into the tube is less, and when your asthma is well controlled, this volume goes up.”

### What can my patient expect?

“This is a simple test that will not make you feel ill.”

### What is my patient’s role?

“We will repeat the test several times today so that we can get an accurate value. We will write it down for you, and you will do it at home. Remember that the values vary during the day, so you need to use it at the same time

every day

every day

In the morning before taking your asthma medication is a good time.

, and write the values down. Eventually, we want to get you to a

'personal best'

'personal best'

This is a patient's best peak expiratory flow, taken when they have no symptoms of asthma and their treatment is optimised.

with which we can compare how your asthma is doing.”

## Preparation

Disinfect the measuring device mouthpiece with an alcohol swab before every demonstration.

## Site & Positioning

Patients should sit or stand up straight for best effect.

## Procedure

1. Slide the marker down to zero.

2. Take a deep breath.

3. Place the mouthpiece between your lips with a tight seal, and hold the measuring device parallel to the ground.

4. Give a quick, sharp exhalation. You do not have to breathe out all the air in your lungs, but breathe out as hard and fast as you can. Do not cough.

5. Record the reading and slide the marker back to zero.

6. Repeat this twice more and circle the highest reading. Your highest reading is the reading you will use.

## Troubleshooting

I'm unsure how I should use these readings.

You can monitor the patient’s asthma control by comparing their PEF with the predicted mean from the graph below, according to the patient’s gender, age and height. The patient’s personal best is a better benchmark than these mean values, and once the patient’s treatment is optimised, you should attempt to record it.

For adults:

For children:

I want my patient to adjust their treatment using their 'personal best'.

Patients should calculate the reading as a percentage of their personal best (new reading/personal best*100). Manage as follows:

80-100% of personal best: continue with current treatment

50-80% of personal best: initiate the

home action plan

home action plan

This is an action plan created by the physician which might include steps such as increasing the dosage of inhaled corticosteroids, increasing the frequency of inhaled short-acting beta agonists, and avoiding smoke and fumes.

.

<50% of personal best: medical emergency. Initiate the home action plan and present for emergency care. Some patients may keep an emergency dose of oral corticosteroids, which they may take on the way to the hospital.

## Risks

1. Patients from a disadvantaged background may struggle to calculate their peak expiratory flow and may not use the device.

## References

1. DeVrieze BW, Modi P, Giwa AO. Peak Flow Rate Measurement. [Updated 2021 Aug 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459325/

2. Adeniyi BO, Erhabor GE. The peak flow meter and its use in clinical practice. Afr J Respir Med 2011;6:5-8.

3. Mash B. How to use a peak expiratory flow meter. In: Mash B, Blitz-Lindeque J, eds. South African Family Practice Manual. 2nd ed. Pretoria: Van Schaik Publishers; 2010: 96-98.