The diaphragm is the chief muscle of inspiration and the most powerful of the respiratory muscles. The diaphragm also serves as a mechanical barrier separating the thorax from the abdomen and maintains the pressure gradient between both compartments (Nason et al. 2012). Under normal conditions, this thin dome-shaped muscular structure acts like a piston within a syringe, generating airflow within airways as its dome descends and enabling tidal breathing. The pressure generated across the dome between the thoracic and abdominal cavities is called the transdiaphragmatic pressure and is proportional to the tension developed within the muscle fibers. Therefore, in terms of physiological meaning, the diaphragm function can be estimated by its capacity to generate this transdiaphragmatic pressure. Diaphragm dysfunction can be associated with the presence of respiratory symptoms, in particular dyspnea, exercise intolerance, and sleep disturbances, and, in the more severe cases, may have a negative impact on survival. Uni- and bilateral diaphragm dysfunction diagnosis and management may be problematic for the clinician because of its relative rarity, its sometimes-subtle clinical manifestations, and difficulties in obtaining a physiologically confirmed diagnosis. As such, diaphragm dysfunction is probably underdiagnosed, but should not be neglected, as it may negatively impact the quality of life, can be a marker of disease severity, and, in some instances such as in the intensive care unit, can be a prognostic marker.