Orthopnea (Greek from ortho, straight + pnoia, breath) is dyspnea which occurs when lying flat, causing the person to have to sleep propped up in bed or sitting in a chair. It is the opposite of platypnoea.
Orthopnea is a symptom of heart failure. It can also occur in those with asthma and chronic bronchitis, as well as those with sleep apnea or panic disorder. The condition is often due to left ventricular failure and/or pulmonary edema. It is also associated with Polycystic Liver Disease.
It is commonly measured according to the number of pillows needed to prop the patient up to enable breathing (Example: "3 pillow orthopnea").