Carbon dioxide retention is a condition that occurs mainly due to respiratory failure and airway obstruction, which leads to insufficient ventilation and reduced oxygenation capacity in the body. The clinical diagnosis of carbon dioxide retention is type II respiratory failure, with the following symptoms: 1. Bulbar conjunctival congestion and edema: patients with carbon dioxide retention may show teary eyes due to dilated conjunctival capillaries; 2. Different degrees of central nervous system symptoms: mild symptoms are the desire to sleep, some patients are disoriented, and severe patients can become comatose, also known as pulmonary encephalopathy. Some patients with chronic carbon dioxide retention can tolerate a partial pressure of carbon dioxide of 100 mmHg, but when the partial pressure of carbon dioxide reaches 60 mmHg, the patient may become comatose, so different degrees of impaired consciousness and even coma are typical symptoms of carbon dioxide retention; 3. Gastrointestinal bleeding: ischemia of the mucosa of the gastrointestinal tract and carbon dioxide retention lead to Dilatation and ulceration of the mucosa of the gastrointestinal tract, resulting in gastrointestinal bleeding; 4. symptoms of metabolic acidosis: patients with carbon dioxide retention will have deep and large breathing and the corresponding symptoms when the metabolic acidosis is severe due to respiratory acidosis; 5. hypoxia: most patients with carbon dioxide retention have ventilation dysfunction, so patients have different degrees of hypoxia. carbon dioxide retention. Therefore, if the oxygen concentration is not paid attention to, high flow oxygenation will instead aggravate carbon dioxide retention and lead to a series of clinical symptoms. In severe cases, central respiratory and cardiac depression and death may occur.