Final answer:
Crackles heard on auscultation of a patient's lungs are caused by air passing through narrow or partially blocked airways. These abnormal lung sounds can be a result of conditions such as pneumonia, asthma, or COPD.
Step-by-step explanation:
Crackles heard on auscultation of a patient's lungs are caused by air passing through narrow or partially blocked airways. These abnormal lung sounds can be a result of conditions such as pneumonia, asthma, or chronic obstructive pulmonary disease (COPD). When the air tries to pass through these constricted or obstructed airways, it creates a crackling sound.