Shortness of breath, or dyspnea, means discomfort or difficulty breathing. Normally, breathing is done automatically. When it becomes laborious, even painful, it is called shortness of breath. The symptoms of shortness of breath may vary depending on the cause: it can be accompanied by a change in respiratory rate, such as an acceleration known as tachypnea, or a deceleration, bradypnea. It can affect the inspiratory time, expiratory time, or both. The most frequent causes of shortness of breath are pulmonary or cardiac in nature, and may be due to asthma, airway obstruction, mainly by a foreign body, an infection or other lung disease, and heart problems such as pulmonary embolism or heart failure. Shortness of breath diminishes or stops when the cause is treated.