What is pleural rub?

• A. Adventitious breath sounds caused by pleural spaces rubbing together.
• B. Crackles from fluid in airways.
• C. Wheezes due to narrowed airways.
• D. Stridor due to obstruction.

Answer: (A)

Pleural rub is an adventitious breath sound produced by friction between inflamed pleural surfaces as the lungs move during breathing. When the pleurae become irritated (pleuritis), the normally slippery surfaces roughen, and their opposing layers rub together, creating a harsh, scratching or grating sound. This sound is often heard during both inspiration and expiration and is typically best heard over the lower lateral or posterior chest, especially when the patient leans forward. It can be accompanied by pleuritic chest pain that worsens with deep breaths.

This distinguishes it from other lung sounds: crackles come from fluid or opening of airways within the airways and alveoli; wheezes are musical sounds from narrowed airways; stridor is a harsh sound from upper airway obstruction. Pleural rub specifically points to inflammation of the pleura rather than airway disease.