What is paroxysmal nocturnal dyspnoea?

• A. Sudden breathlessness developing 2-5 hours after sleep, relieved by sitting upright.
• B. Chronic morning breathlessness that improves with activity.
• C. Breathlessness only when lying flat during the day.
• D. Shortness of breath that occurs exclusively during exercise.

Answer: (A)

Paroxysmal nocturnal dyspnea is the sudden, severe shortness of breath that wakes you from sleep after a few hours (typically 2–5 hours) and is relieved by sitting up. It happens because when you lie flat, venous blood returns more readily to the heart, increasing pressure in the lungs and causing fluid to leak into the air spaces (pulmonary edema) in people with heart failure or fluid overload. Sitting up helps by reducing venous return and easing breathing.

This pattern is different from other forms of dyspnea. Breathlessness that only occurs when lying flat during the day describes orthopnea, not nocturnal episodes. Shortness of breath during exercise is exertional dyspnea, which occurs with activity. Chronic morning breathlessness that improves with activity describes a different, more persistent pattern that isn’t tied to sleep.