Dyspnea is among the most common symptoms in patients with respiratory diseases such as Asthma, chronic obstructive pulmonary disease (COPD), Fibrosis, and Pulmonary Hypertension. However, the pathophysiology and underlying mechanisms of dyspnea in patients with respiratory diseases are still poorly understood. Diaphragm dysfunction might be highly prevalent in patients with dyspnea and respiratory diseases. The association of diaphragm function and potential prognostic significance in patients with respiratory diseases has not yet been investigated.