How does the hospital check your lungs to see if they are healthy?

Several ways...: There are several ways to check the status of your lungs. Physical exam and auscultation (listening with a stethoscope) are good starting points. Chest x-ray is a valuable tool. Sometimes additional imaging such as a ct scan might be performed. Lab tests and cultures of material/cells from the lungs (such as a deep sputum) might also help.