Breathing and lung function tests

Respiratory muscle tests

What is it?

Respiratory muscle tests measure how much pressure your breathing muscles can generate when you breathe in or out.

What happens during the test?

Sometimes a handheld device with a mouthpiece is used. Alternatively a fixed piece of equipment in a lung function lab can be used. Your health care professional will explain how you should breathe:

Mouth pressures

  • to measure the strength of the muscles that help you breathe in, you will be asked to breathe out as long as you can and then suck hard on a mouthpiece for at least 1 second. This is the maximum inspiratory pressure.

  • 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 mouthpiece. This is the maximum expiratory pressure.

Sniff pressures

For these a small probe is placed to block one of your nostrils. It measures the pressure while you sniff as hard as you can.

The lung specialist may also ask you to do a spirometry test lying down to see if this makes your lung capacity fall (a sign of muscle weakness).

What will the result look like?

You will usually have to repeat each test a few times to make sure the results are as good as you can get.

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Last medically reviewed: February 2017. Due for review: February 2017

This information uses the best available medical evidence and was produced with the support of people living with lung conditions. Find out how we produce our information. If you’d like to see our references get in touch.