Respiratory muscle strength is an important part of lung function. Assessment of the respiratory muscles' ability to generate force is important for recognizing respiratory muscle weakness in both sick and healthy people.

The simple non-invasive tests of respiratory muscle strength are essential in monitoring patients with chronic obstructive pulmonary disease (COPD) who are undergoing a program of lung rehabilitation and are also useful in the assessment of selected patients, most commonly those with neuromuscular diseases such as amyotrophic lateral sclerosis (ALS), multiple sclerosis, myasthenia, myopathies or unexplained breathlessness.

It is necessary to measure the maximum inspiratory and expiratory pressures for early diagnosis of respiratory muscle weakness and for follow up the effectiveness of any neurological treatment.