1. Respiratory diseases: Cough can be caused by irritant gas inhalation from various parts of the respiratory tract, such as the pharynx, larynx, trachea, bronchi and lungs, and by stimulation by foreign bodies, inflammation, tumors and bleeding. 2. Pleural diseases: cough can be caused by pleurisy or when the pleura is irritated (e.g. spontaneous pneumothorax). 3, heart disease: cough can be caused by pulmonary stasis and pulmonary edema caused by mitral stenosis or other causes of left heart insufficiency. Coughing and hemoptysis can also occur when pulmonary embolism is caused by dislodged emboli in the right heart or body circulation veins. 4. Central factors: Cough can also originate in the cerebral cortex (random cough), when impulses are sent from the cerebral cortex to the cough center in the medulla oblongata, causing a coughing action. What are the characteristics of cough in relation to its etiology? 1. Nature of cough A cough without sputum or with very little sputum is called a dry cough and is commonly seen in the early stages of acute pharyngitis and acute bronchitis, pleurisy, and mild tuberculosis. A cough with sputum is called a wet cough and is commonly seen in pneumonia, chronic pharyngitis, chronic bronchitis, bronchiectasis, lung abscess and cavitary tuberculosis. 2. The timing and rhythm of coughing Sudden coughing is mostly caused by acute upper respiratory tract inflammation (especially those caused by irritant gas inhalation) and foreign bodies in the trachea or bronchi. Long-term chronic cough is most often seen in chronic respiratory diseases, such as chronic bronchitis, bronchiectasis, chronic lung abscess, and cavitary tuberculosis. Episodic cough can be seen in cases such as whooping cough, bronchial lymph node tuberculosis or cancerous tumors compressing the bifurcation of the trachea. In chronic bronchiectasis and lung abscess, the patient’s cough often intensifies in the early morning or at night when lying down (i.e., when changing position), followed by sputum production. 3. The tone of the cough The hoarseness of the cough is caused by inflammation of the vocal cords or tumors, which can be seen in laryngitis, laryngeal tuberculosis, and laryngeal cancer. A barking cough is most often seen in the epiglottis, laryngeal disorders or tracheal compression. A muffled cough is seen in patients with extreme weakness or vocal cord paralysis. Metallic tone cough can be due to mediastinal tumors, aortic aneurysms or bronchial carcinoma, etc. as a result of direct compression. 4. Accompanying symptoms of cough: Those with fever are often due to respiratory tract infection, bronchial dilatation complicated by infection, pleural inflammation, etc. Those with chest pain can be seen in pneumonia, pleurisy, bronchial cancer, spontaneous pneumothorax, etc. Those with weight loss should pay attention to tuberculosis, bronchial carcinoma (primary lung cancer), etc. Respiratory distress is commonly associated with severe heart and lung diseases, massive pleural effusion, spontaneous pneumothorax, etc. Those with croup can be seen in bronchial asthma, spasmodic bronchitis, cardiogenic asthma, endotracheal foreign body, etc. Those with pestle finger can be seen in bronchiectasis, chronic lung abscess, etc.