Dyspnea, shortness of breath (SOB), or air hunger, is the subjective symptom of breathlessness. It is a normal symptom of heavy exertion but becomes pathological if it occurs in unexpected situations. In 85% of cases it is due to either asthma, pneumonia, cardiac ischemia, interstitial lung disease, congestive heart failure, chronic obstructive pulmonary disease, or psychogenic causes. Treatment typically depends on the underlying cause.