Mechanical ventilation: commonly known as ventilator, is a device that can replace, control or change the normal physiological breathing of a person, increase lung ventilation, improve respiratory function, reduce respiratory work consumption, and conserve the reserve capacity of the heart. Ventilator is an important measure that has been widely used in recent years during the resuscitation of patients with acute and critical illnesses. Possible complications: Lung injury: causing interstitial emphysema, pneumothorax, mediastinal emphysema, subcutaneous emphysema, etc. Hypovolemia, shock, decreased cardiac output: mostly due to ① Positive pressure ventilation causes obstruction of venous return and decreased return blood flow. (ii) Elevated alveolar pressure, compression of the vascular bed, and increased right ventricular load. ③ positive pressure ventilation causes the heart and large blood vessels to be pressurized, and the heart is restricted in diastole, etc. all cause hypotensive shock and decreased cardiac output. Arrhythmia: Various arrhythmias can occur, with atrial being the most common. It is related to acidosis, hypoxia, hypercapnia, electrolyte disorders and drugs. Gastrointestinal distention and gastrointestinal bleeding: Gastrointestinal bleeding is mostly caused by radical ulcers, gastric mucosal stasis, hypoxia, hypercapnia, etc. or pre-existing gastrointestinal lesions. Pulmonary infection. Pulmonary atelectasis. Deep venous thrombosis: prolonged bed rest in a fixed position reduces and slows down venous reflux and predisposes to the formation of deep venous thrombosis. Nutritional and metabolic abnormalities: reduction in mechanical ventilation feeding occurs hydropower acid-base imbalance, mechanical ventilation leads to increased secretion of antidiuretic hormone, increased intrathoracic pressure, blocked lymphatic return, and increased capillary pressure in body circulation, resulting in increased lymphatic fluid production. Impaired renal function or excessive infusion of fluids after ventilator application cause water and sodium retention.