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 the mouth pressure test easier, and some find the sniff pressure test easier. You will 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 and measures how strong the muscle below your lungs is (the 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, and then suck hard on a mouthpiece for at least one second. It will feel like sucking a very thick drink through a straw. This is the maximal inspiratory pressure (written in your results as PI_max or MIP).

Checking the strength of the muscles that help you breathe out

To check how strong the muscles are that help you breathe out, you’ll be asked to breathe in deeply first and then blow out as hard as you can into a closed off mouthpiece. This is the maximal expiratory pressure (written in your results as PE_max or MEP).

In a sniff pressure test one of your nostrils is blocked off. You then sniff as hard as you can with the open/other nostril. The test measures the pressure when you sniff. The sniff pressure test also looks at the strength of the muscles that help you breathe in. It may be written in your results as SNIP. 

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