Orthopnea is dyspnea
(shortness of breath) that occurs while lying down. Orthopnea is often a sign of heart failure
, and this symptom should always be evaluated by a physician. Orthopnea occurs because when a patient with heart failure lies down, fluid that has pooled in the legs during the day is redistributed and begins to accumulate in the lungs.
People with orthopnea often compensate -- sometimes subconsciously -- by sleeping on several pillows in order to keep their head elevated and thus reduce their symptoms. This is why doctors will often ask patients with heart failure how many pillows they use at night.