It is an area of internal medicine that deals with bronchial tubes, lungs, and pleura related to respiration. It deals with infectious diseases such as pneumonia, tuberculosis, and bronchiectasis, chronic obstructive lung diseases such as asthma, emphysema and chronic bronchitis, intrathoracic tumors including lung cancer and mediastinal tumor, various pleural diseases, lung fibrosis and interstitial lung disease and sleep apnea (disease in which respiration is repeatedly ceased for at least 10 seconds during sleep while snoring).