The principle of transnasal invasive airway-free positive pressure ventilation for sleep apnea pressure support ventilation (PSV) is a transoral mask, triggered by the patient’s voluntary breathing, that applies a predetermined positive pressure support in the inspiratory phase to assist the patient’s inspiratory activity.CPAP is a positive end-expiratory pressure with adequate voluntary breathing. Compared with positive end-expiratory pressure, CPAP not only significantly reduces the patient’s work of breathing, but also serves to prevent atrophy, increase functional residual air volume, improve lung compliance and dilate the upper airway. Long-term application of CPAP can improve the sensitivity of the central nervous system to low oxygen and high CO2, and improve the respiratory regulation of the nervous system. I. The basic composition of continuous positive pressure ventilation (CPAP) machine CPAP machine consists of two parts: treatment system and humidifier. 1, the treatment system consists of three parts: the main body, the tube and the mask. The main body generates the pressure for treatment, and the rotational speed of the turbine blades determines the size of the treatment pressure. The pressure generated by the main unit is transmitted to the nasal mask through the tube, and finally the positive pressure gas is physically supported by the nasal mask through the nasal cavity to the patient’s upper airway. There are many types of portable ventilators with similar performance, and it is important to be familiar with the performance and use of each type of ventilator. Mouthpiece mask and fixation device: It is an important factor that affects the comfort level of the patient during treatment and whether there is air leakage. They should be selected according to the different facial shapes and nasal profiles of patients. The patient can tolerate a small amount of nasal mask leakage under the condition of ensuring sufficient tidal volume (≥7ml/kg). If gastric distension is present, a gastric tube may be placed. If the patient’s nasal resistance exceeds 5 cmH2O/(L?S), it can affect the patient’s nasal ventilation effect. Generally, the dead space of oral and nasal mask is about 250ml, and the dead space of nasal mask is about 50~100ml. 2.Humidifier is the standard configuration of CPAP, there are two types: ① Natural evaporation type: the positive pressure gas generated by CPAP passes through the humidifier, and the water evaporates naturally to humidify the gas; ②Heatable constant temperature type: the water in the humidifier increases volatilization through heating, so that the gas is humidified and heated. The CPAP system consists of motor, fan and sensor control parts as well as external catheter and nasal mask, the main unit generates sufficient airflow to form positive pressure through the resistance in the system, and the pre-set positive airflow is fed into the patient’s upper airway through the catheter and nasal mask. The CPAP system can also compensate for small air leaks (including mask or oral leaks) by increasing flow to maintain a stable positive upper airway pressure. This is the mechanism of action of CPAP for OSAHS. It has been hypothesized that CPAP maintains upper airway opening during sleep state by increasing the reflex of end-expiratory lung volume. It has also been suggested that CPAP treatment inhibits the electromyographic activity of the upper airway diastolic muscles. An “airway pull” mechanism has been proposed: pulmonary distention of cervical tissues can affect the random opening of the upper airway. Although upper airway resistance varies with lung volume, this effect is relatively small.