Diaphragm dysfunction is defined as the partial or complete loss of diaphragm muscle contractility. However, because the diaphragm is one of only a few skeletal muscles that is not amenable to direct examination, the tools available for the clinician to assess diaphragm function have been limited. Traditionally, measures of lung volume, inspiratory muscle strength, and radiographic techniques such as fluoroscopy have provided the major method to assess diaphragm function. Measurement of transdiaphragmatic pressure provides the most direct means of evaluating the diaphragm, but this technique is not readily available to clinicians. Diaprhragm ultrasonography is new method that allows for direct examination of the diaphragm.