Pleural friction rub is

• A. A grating or creaking sound caused by inflamed pleural surfaces rubbing against each other
• B. A high-pitched whistling sound
• C. Low-pitched rumble
• D. A cracking sound in alveoli

Answer: (A)

Pleural friction rub is the harsh, grating or creaking sound heard when the inflamed pleural surfaces (the visceral and parietal pleura) rub against each other during breathing. This sound comes from roughened, inflamed pleura sliding together as air moves in and out, and is often best heard with the patient sitting up or leaning forward and the stethoscope placed on the chest wall. It can be more noticeable with shallow breaths and may be present on both inspiration and expiration.

This is different from a high-pitched whistling sound, which suggests a wheeze from narrowed airways; a low-pitched rumble, which points to secretions causing rhonchi; and a cracking sound in the alveoli, which describes crackles (rales) from air reopening in collapsed or fluid-filled alveoli.