Ventilator is a kind of instrument that can replace the artificial independent breathing, the ventilator can play the role of replacing human respiratory muscles, replacing the human respiratory central nervous system, and meet the role of respiratory metabolism and so on. 1. Replacing human respiratory muscles: the ventilator can provide the power to deliver gas, thus replacing the respiratory muscles of the human body. 2. Replacing the human respiratory central nervous system: the ventilator can produce a certain respiratory frequency and respiratory ratio, which can replace the respiratory central nervous system to dominate the respiratory rhythm function. 3. Satisfy the respiratory metabolism: the ventilator can provide the appropriate minute ventilation or tidal volume, which can fully satisfy the needs of human respiratory metabolism. 4. Other: Ventilator can make patients feel comfortable during sleep and can play a role in improving sleep quality. It can also improve the patient’s respiratory function by increasing the sensitivity of the patient’s central system to oxygen. Ventilators are generally categorized into non-invasive ventilators and invasive ventilators, and patients should choose them according to their condition under the guidance of their doctors.