Orthopnea is due to increased distribution of blood to the pulmonary circulation when a person lies flat or closer to a horizontal position. Under such circumstances, patients may describe shortness of breath when they bend over (e.g. From a neuromuscular perspective, orthopnea is potentially a sign of severe diaphragmatic weakness. It is also as associated with polycystic liver disease.
It can also occur in those with asthma and chronic bronchitis, as well as those with sleep apnea or panic disorder. Orthopnea is often a symptom of left ventricular heart failure and/or cardiogenic pulmonary edema. Orthopnea is the opposite of platypnea, shortness of breath that worsens when sitting or standing upright. It is also seen in cases of abdominal obesity or pulmonary disease. It is commonly seen as a late manifestation of heart failure, resulting from fluid redistribution into the central circulation, causing an increase in pulmonary capillary pressure and causing difficulty in breathing. Orthopnea or orthopnoea is shortness of breath (dyspnea) that occurs when lying flat, causing the person to have to sleep propped up in bed or sitting in a chair.
