Incentive spirometry is a form of respiratory therapy designed to improve lung capacity and bronchial hygiene. The principle behind IS (also known as "sustained maximal inspiration" or "SMI") is to provide visual feedback to a patient as a means of improving their respiratory effort.

To accomplish this, the incentive spirometer, the device used, is designed to show a clear numbered scale to the patient for an objective measure of their effort and progress. IS is used in many different settings, but the most common are:

The procedure to perform IS is simple. The mouthpiece is inserted, the patient exhales completely, then inhales at the most rapid rate they can sustain. The spirometer measures the flow rate and an indicator moves to the appropriate number on the scale (generally measured in ml/sec). The patient may try one or more times.

IS is most often ordered hourly in an inpatient health care setting. On an outpatient basis, it is used bt asthmatics to check on the necessity of dosing their medications early, or of using a higher dose. Overall, IS is simple, inexpensive, and effective, and a good addition to many respiratory treatment regimens.