Paroxysmal nocturnal dyspnea differs from orthopnea how?

• A. Occurs during the day
• B. Resolves immediately upon sitting up
• C. Occurs during sleep and may not subside when upright
• D. Is not related to LV decompensation

Answer: (C)

Paroxysmal nocturnal dyspnea is a nocturnal manifestation of left-sided heart failure. It wakes you from sleep with sudden breathlessness due to fluid that has pooled in the legs during the day and is redistributed into the lungs when you lie down. The resulting pulmonary edema often improves only after you sit up and may even linger for a while, so relief isn’t always immediate with upright posture. Orthopnea, on the other hand, is dyspnea that appears when lying flat and is typically relieved promptly by sitting up or standing. The key distinction is the timing (during sleep for the nocturnal form) and the sometimes incomplete or delayed relief with upright position, reflecting how nocturnal fluid shifts and pulmonary edema evolve in PND.