Laryngeal edema is an infiltration of tissue fluid under the mucosa in the laryngeal laxity. Its etiology is of two main types: infectious and non-infectious. Infectious laryngeal edema can be caused by acute laryngitis, acute epiglottitis, acute laryngeal chondromyelitis, laryngeal abscess, laryngeal tuberculosis, laryngeal syphilis, and other acute purulent inflammatory diseases of the pharynx or neck. Non-infectious laryngeal edema can be caused by heart disease, nephritis, liver cirrhosis, hypothyroidism, allergic or hereditary such as injection of penicillin, oral administration of drugs such as potassium iodide and aspirin, and consumption of allergenic foods such as fish, shrimp and crab by allergic individuals. The common causes of laryngeal edema are as follows: 1. Mechanical injury of tracheal intubation, such as rough operation, too thick and too hard catheter, too much pressure of the balloon to damage the airway mucosa, as well as improper position, many intubations or poor fixation of the intubation, which makes the intubation move up and down, can increase the chance of trauma, and Wylie reported a case of laryngeal granuloma in 15 min of intubation, which indicates that trauma of intubation is the main factor. 2, upper respiratory tract infection The original upper respiratory tract inflammation is not completely controlled, the catheter sterilization is not strict, the secretion around the cannula is retained, and the nasal cavity is easy to bring the nasal bacteria into the airway when the nasal cannula is inserted. Due to the narrow vocal canal, loose mucosal tissue and rich lymphatic vessels in children, vocal canal obstruction can occur with mild inflammation and edema, causing inspiratory dyspnea. 3.Allergy or excessive input of crystalloids After contact with exogenous allergens such as certain drugs, food or contacts, the body is in a sensitized state, and when the body is exposed again, type I allergic reaction occurs, which can cause laryngeal edema if the target organ is the pharynx. In addition, due to changes in the composition of prefilled fluid, colloid osmotic pressure or excessive infusion and low water regulation, fluid retention often occurs in infants and children after extracorporeal circulation, resulting in bulbar conjunctival edema and edema in the larynx where the mucosal tissue structure is relatively lax.