Which statement best describes the difference between wheezes and crackles on auscultation?

• A. Wheezes are discontinuous popping sounds; crackles are continuous musical sounds.
• B. Wheezes are heard only with inspiration; crackles only with expiration.
• C. Wheezes are associated with consolidation; crackles with asthma.
• D. Wheezes are continuous musical sounds; crackles are discontinuous popping sounds.

Answer: (D)

Wheezes and crackles are distinguished by whether the sound is continuous or discrete. Wheezes are continuous, musical sounds produced as air flows through narrowed or inflamed airways; they often have a high pitch and are heard mainly during expiration, though they can occur on inspiration as well. Crackles are discontinuous, popping sounds that come from the sudden opening of small airways or alveoli, usually most noticeable on inspiration. This difference in continuity and the underlying mechanism is why the statement describing wheezes as continuous musical sounds and crackles as discontinuous popping sounds is the best choice. Other options mix up timing or what the sounds indicate, which doesn’t fit the typical patterns of wheezes versus crackles.