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Respiratory Muscle Pressure Assessment

If your doctor wants to evaluate the strength of your respiratory muscles, he will request an assessment of your maximal respiratory pressures. The test measures the force generated by the diaphragm and chest muscles when you forcefully breathe in and out.

Neuromuscular diseases, such as muscular dystrophy or multiple sclerosis, can weaken the muscles you need to help you breathe.

The laboratory also refers to this test as maximum inspiratory and expiratory pressure measurements.


The evaluation takes about 20 minutes.


Test Preparation



You may generally continue with your normal routine. However, there are some points to note to improve comfort and ensure accurate results:

Refrain from smoking for as long as possible before the test
Avoid tight clothing
Avoid a heavy meal 2 hours before the test
Do not drink alcohol for at least 4 hours before the test
Avoid vigorous exercise for a few hours before the test
If you use an inhaler please bring it with you


Test Procedure



The respiratory Physiologist will instruct you to seal your lips firmly around a mouthpiece and ask you to exhale slowly and completely, and then "pull in hard, like you are trying to suck up a thick milkshake."

This maneuver will be fully explained and demonstrated to you and you might be asked to repeat it.

You will be asked to maintain your inspiratory pressure for at least 1.5 to 2 seconds.

You will be allowed to rest for about one minute and then repeat the maneuver five times in order to obtain accurate and reproducible results.

After 5 minutes rest, your expiratory muscle pressure will be assessed. You will be asked again to seal your lips firmly around a mouthpiece and ask you to inhale slowly and completely, and then "blow in hard, like you are trying to blow to unblock a blocked tube". You will be asked to keep this pressure for at least 1.5 to 2 seconds. You will be allowed to rest for about one minute and then repeat the maneuver five times in order to obtain accurate and reproducible results.


Risks involved



The evaluation of the maximum inspiratory (MIP) and expiratory pressure (MEP) measurements is generally a safe test. You may feel short of breath or dizzy for a moment after you perform the test.

Because the test requires some exertion, it is not performed if you have had a recent heart attack or some other heart conditions. Rarely, the test triggers severe breathing problems.

If you have any of the following please call us to discuss:

  • Unstable angina
  • A recent pneumothorax (air trapped beneath the chest wall)
  • A recent heart attack or stroke
  • Recent eye or abdominal surgery
  • Coughed up blood recently and the cause is not known 

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