Respiratory pressure meter

The principal advantage of volitional tests is that they give an estimate of inspiratory or expiratory muscle strength, are simple to perform, and are well tolerated by patients.

In patients with multiple sclerosis for example, abdominal (and hence expiratory) muscle weakness is a hallmark of the disease, and is related to clinical problems such as mucus retention.

[6] This test is performed at RV (Residual Volume), the amount of air remaining in the patient's lungs after fully exhaling.

The patient then inhales as hard and as fast as possible with maximal sustained effort for longer than 1 second, and the pressure is the highest achieved during that time.

This test is particularly suited to neuromuscular weakness because it doesn't require a mouthpiece and because it is easily mastered by the vast majority of patients.