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Bubble PEP (Positive Expiratory Pressure)

What is Bubble PEP (Positive Expiratory Pressure)?

PEP stands for positive expiratory pressure. Bubble PEP is a treatment to help children who have a buildup of mucus in their lungs.

Bubble PEP is used for any child who has difficulty clearing mucus, most commonly those with cystic fibrosis (CF) or those who have just had surgery. During treatment, your child will be encouraged to blow big bubbles through water – which is fun!

The equipment used is shown in the diagram; treatment is explained in the next section below.

Bubble PEP equipment. 

Bubble PEP Equipment

Your child will be encouraged to blow down the tubing into the water, and make bubbles. This creates positive pressure back up the tubing and into your child’s airways and lungs.

As the pressure holds open your child’s airways, it helps more air to move in and out of the lungs. The air flow helps to move mucus out of the lungs into the airways. From here, it can be coughed up (cleared), which is the aim of treatment.



1. Fill the bottle with _______ water and about five squirts of liquid soap, plus food coloring if you want colored bubbles.

2. Put the plastic tubing into the water, through the top of the bottle.

3. Put the bottle into a tray or bowl.

Performing Bubble PEP Treatment

1. Ask your child to take a breath in and then blow out through the tubing, into the water to create bubbles. The breath out should be as long as possible. Aim to get the bubbles out of the top of the bottle each time; it may be messy and should be fun!

2. Repeat _______ times. This is one cycle.

3. Ask your child to huff (forced expiration technique) and cough to clear the mucus, as taught by your respiratory therapist. Encourage your child to cough the mucus out rather than swallow it.

4. Repeat this cycle (steps 1-3) ____ times in total.

5. The tubing, bottle and tray should be washed out and left to dry or dried with a disposable towel and stored in a clean place until next used. You should throw the bottle and tubing away, replacing it with clean equipment, at least once a week.

Associated Risks of Bubble PEP

There is a minor risk that your child may bleed within his or her airways when doing bubble PEP. If you notice any blood (red flecks) in your child’s mucus, you should stop using bubble PEP and ask for advice from your doctor or the cystic fibrosis (CF) team.

There is also a slight risk of damage to the lung surface when using bubble PEP. If your child becomes suddenly breathless or has pain, stop and contact the CF team.

Last Updated 03/2020

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