Why does the air pressure on my CPAP machine feel like it changes as I breathe?Updated 17 days ago

If it feels like the air pressure from your CPAP machine gets stronger when you inhale and weaker when you exhale, this is usually completely normal. It’s caused by a comfort feature found in most modern CPAP machines called expiratory pressure relief.

✅ What is Expiratory Pressure Relief (EPR, Flex, or similar)?

Depending on the brand, this feature may be called:

• EPR (ResMed)

• C-Flex/A-Flex (Philips Respironics)

• Pressure Relief or similar (on other models)

No matter the name, the function is the same:

• It slightly lowers the pressure when you breathe out to make exhaling more comfortable.

• It returns to your prescribed pressure as you inhale to keep your airway open.

This can feel like the airflow is changing strength with each breath—but it’s a normal part of how many machines improve comfort.

Can I turn it off or adjust it?

Yes! Most machines allow you to adjust or disable this setting based on your preference:

1. Go to your CPAP machine’s comfort or settings menu.

2. Look for options labeled EPR, Flex, or Pressure Relief.

3. You can typically choose:

   • Off – consistent pressure during inhale and exhale

   • 1–3 – levels of relief, with 3 being the most noticeable

⚠️ Some machines may require access to the clinical settings menu. If you're unsure how to adjust this, feel free to contact us.

Still unsure or need help?

Email us at [email protected] with your machine model, and we’ll walk you through the settings or help determine if something else may be going on.