Which statement accurately differentiates crackles and wheezing?

• A. Wheezing is a high-pitched whistling sound from narrowed airways
• B. Crackles are continuous wheeze
• C. Wheezing is due to fluid in alveoli
• D. Crackles only occur in pneumonia

Answer: (A)

Wheezes are high-pitched, musical sounds produced by turbulent airflow through narrowed airways. This narrowing—often from bronchospasm or inflammation—creates a whistling quality, most noticeable during expiration and sometimes during inspiration in more severe obstruction. Crackles, on the other hand, are brief, discontinuous popping sounds heard mainly on inspiration. They come from the sudden reopening of small airways or from fluid in the alveoli, and they’re not continuous like wheezes.

That’s why the statement about wheezing being a high-pitched whistling sound from narrowed airways is the best description. The other choices mix up the origins and acoustics: crackles are not continuous wheeze (they’re discrete pops), wheezing is not due to fluid in the alveoli (that’s crackles), and crackles can appear in many conditions beyond pneumonia (such as edema or atelectasis).