Respiratory muscle tests

Respiratory muscle tests tell you how well the muscles around your lungs work.

There are two types of respiratory muscle tests:

• mouth pressure tests
• sniff pressure tests.

Some people find it easier to do the mouth pressure test, while others prefer the sniff pressure test. You’ll usually have to repeat each test a few times to make sure the results are as good as you can get.

Your doctor may also ask you to do a spirometry test both lying down and sitting up. This is sometimes called positional spirometry. It measures the strength of the muscle below your lungs (diaphragm).

Mouth pressure tests measure the strength of the muscles that help you breathe in and out.

Checking the strength of the muscles that help you breathe in

You’ll be asked to breathe out for as long as you can. Then suck hard on a mouthpiece for at least one second. It will feel like sucking a very thick drink through a straw.

This measures the maximal inspiratory pressure. It will be written in your results as PI_max or MIP.

Checking the strength of the muscles that help you breathe out

You’ll be asked to take a deep breathe first. Then you’ll blow out as hard as you can into a closed off mouthpiece.

This measures the maximal expiratory pressure. It will be written in your results as PE_max or MEP.

Sniff pressure tests measure the pressure when you sniff. The sniff pressure test also looks at the strength of the muscles that help you breathe in.

One of your nostrils will be blocked using a small, soft plug. You’ll then be asked to sniff as hard as you can with the other nostril.

This measures the sniff nasal inspiratory pressure. It may be written in your results as SNIP.

Results will be different for everyone. They’ll depend on your age and sex. Your doctor will explain your results and the next step for your treatment.