Final answer:
The fourth step in checking lung sounds is to have the patient breathe deeply to allow the clinician to better listen to airflow and heart murmurs during auscultation using a stethoscope.
Step-by-step explanation:
The fourth step to checking lung sounds in a patient is typically to ask the patient to breathe deeply during auscultation. This helps the clinician to better listen to airflow and can amplify certain heart murmurs. Inhalation and exhalation can affect the audibility of murmurs on either side of the heart due to changes in blood flow, so it's crucial for the clinician to listen carefully during both phases of breathing. The right placement of the stethoscope's bell is also imperative for optimal auscultation.