Which breath sound indicates alveolar fluid?

• A. Wheezes on expiration
• B. Rhonchi
• C. Stridor
• D. Fine crackles (rales) on inspiration

Answer: (D)

Fine crackles heard during inspiration indicate fluid in the alveoli. When alveolar spaces fill with fluid, the tiny airways reopen with each breath, producing a delicate, high-pitched popping sound—the crackles. This is a hallmark of alveolar fluid, as seen with pulmonary edema or inflammatory processes in the lungs. The sound is typically best heard on inspiration and can be felt more at the bases of the lungs. By contrast, wheezes on expiration come from narrowed airways, rhonchi are secretions in larger airways, and stridor signals an upper airway obstruction. So the presence of fine crackles on inspiration most strongly points to alveolar fluid.