The main cause of injury above the tracheal ridge is inhalation injury, which is related to the environment that causes injury. It often occurs in the non-ventilated or confined environment, especially when the explosion combustion, this environment, the concentration of hot flame, high temperature, not easy to spread quickly, coupled with the confined space, incomplete combustion, generating a large number of carbon monoxide and other toxic gases, so that the patient is poisoned and coma, serious asphyxiation death. When combined with explosive combustion, high temperature, high pressure, high flow rate of air and thick toxic gases can cause damage to the deep respiratory tract and lung parenchyma. In addition, the patient standing or running and shouting, resulting in hot flame inhalation, is also one of the causes of injury. So what is the diagnosis about the injury above the tracheal ridge due to inhalation injury? 1, direct injury to the respiratory tract by heat Heat includes both dry heat and moist heat. Flames and hot air belong to dry heat, and hot vapor belongs to wet heat. When exhaling hot air, the vocal cords can be reflexively closed, while the dry hot air has a poor heat transfer capacity, the upper respiratory tract has a hydrothermal exchange function, which can absorb a lot of heat to make it cool; dry hot air reaches the bifurcation of the bronchial bulge, the temperature can drop to 1/5 to 1/10 of the original. so dry heat often causes damage to the upper respiratory tract. Humid hot air than dry hot air heat capacity is about 2000 times greater than dry air, the conduction capacity is about 4000 times greater than dry air, and slow heat dissipation, so in addition to causing upper respiratory tract injury and tracheal injury, but also to bronchial and lung parenchymal injury. 2, harmful substances to the respiratory tract injury inhalation smoke, in addition to particles, there are a large number of harmful substances, including carbon monoxide, nitrogen dioxide, sulfur dioxide, nitrogen peroxide, hydrochloric acid, cyanuric acid, aldehydes, ketones, etc.. These substances can cause direct damage to the respiratory tract through thermal effects. Toxic gases can stimulate laryngeal and bronchial spasm and have chemical damage to the respiratory tract. Water-soluble substances such as ammonia, chlorine, sulfur dioxide, etc. can cause chemical burns when combined with water to become acid or base. Nitrides in the respiratory mucosa can react with water and salt to produce nitric acid and nitrite, the former directly corrodes the respiratory tract, the latter is absorbed and combined with hemoglobin to form methemoglobin, causing tissue hypoxia. Cyanuric acid can make cytochrome oxidase lose its oxygen delivery effect and inhibit intracellular respiration. Aldehydes can reduce cilia activity, reduce alveolar macrophage activity, damage capillaries and cause pulmonary edema. The acrolein content in the smoke produced by polyurethane combustion is about 50 ppm, and chemical respiratory damage and pulmonary edema can occur if 5.5 ppm of acrolein is inhaled, and 10 ppm can cause death in a few minutes. The toxicity of hydrogen cyanide and carbon monoxide are additive. When the temperature rises to 1000℃, polyurethane foam decomposes and produces a large amount of hydrogen cyanide, which can cause death when the concentration of cyanide in the blood serum reaches 100mol/L.