Which term refers to difficulty breathing while lying down?

• A. Abnormal rhythm of the heart
• B. Difficulty breathing while lying down
• C. Chest pain due to hypoxemia of the heart
• D. A moving clump of platelets

Answer: (B)

Orthopnea is the term for difficulty breathing when lying down. The reason it occurs is that lying flat increases venous return to the heart, raising preload. In left-sided heart failure or fluid overload, this extra return raises pressures in the pulmonary veins, leading to pulmonary congestion and shortness of breath. Sitting up or propping the head reduces venous return and pulmonary congestion, easing breathing. Many patients with orthopnea also experience paroxysmal nocturnal dyspnea, waking at night with breathlessness. This symptom is a clue to heart failure or volume overload. The other descriptions point to different issues (an abnormal heart rhythm, chest pain from ischemia, or a moving platelet clump) and do not capture the specific breathing difficulty that occurs when lying down.