1.Reduce the incidence of ventilator-associated pneumonia (VAP) Usually, patients who need mechanical ventilation are in critical condition. At this time, the immune ability of the body has been seriously reduced. However, due to tracheotomy or intubation, the respiratory tract has lost its function of heating and humidifying the inhaled air, which is extremely easy to cause endogenous infection. Respiratory secretions may increase due to stimulation of tracheal intubation, so it is necessary to strengthen sputum aspiration treatment for patients with artificial airway mechanical ventilation. However, since sputum aspiration is an invasive operation, it is of great significance to take effective sputum aspiration measures at this time to prevent or reduce respiratory infection. Closed sputum aspiration The whole process of sputum aspiration is carried out in a closed environment, which avoids the repeated opening of the ventilator pipe with open sputum aspiration and increases the chance of cross-infection. At the same time, in the process of sputum aspiration, it will not cause environmental pollution due to the patient's choking and spouting, so as to avoid cross-infection and reduce the occurrence of adverse reactions. 2.Maintain effective ventilation and prevent hypoxemia Sputum suction in the implementation of the open when the breathing machine must be disconnected, although before the sputum suction give the patients with sufficient oxygen and pulmonary ventilation, but during the sputum suction from breathing machine can reduce patients with alveolar gas exchange capacity, increase its risks, let patients with pulmonary gas exchange is more difficult, lead to significantly reduce the lung capacity, breathe out at the end of the positive pressure loss, thus patients can't keep good oxygenation, heart rate, and reduce adverse reactions such as arterial blood oxygen saturation. However, once hypoxemia occurs, the time needed to restore the blood oxygen content to the normal value is significantly increased, up to about 11 minutes, which poses a corresponding threat to the patient's life safety. Closed sputum aspiration can be carried out without cutting off the ventilator, which can effectively reduce the lung volume reduction and alveolar atrophy caused by sputum aspiration, and prevent the imbalance of ventilation and blood flow ratio caused by alveolar atrophy. In this way, the sheer force caused by alveolar atrophy and extension can be alleviated, and the re-damage of lung tissue can be avoided or reduced. 3.Because the closed sputum suction tube avoids disconnection of the ventilator during sputum suction, thus interrupting the continuous airway humidification, it can ensure the continuous humidification and heating of the ventilator. 4.Prevent occupational exposure of medical staff Sputum suction for both the patients and the medical personnel are the source of infection, patients with respiratory pathogens can be produced at a speed of 120 km/h, cause easily when they are in the wet airway in patients with cough, sputum sometimes spray to the medical staff, the face, on the medical staff occupational injuries, closed suction phlegm have complete closure, can avoid choking cough caused by sputum aspiration in patients sputum, pollution medical personnel hand, clothes, and bed unit, reduce the cross-infection, to ensure the safety of the medical staff. 5.For patients with a high frequency of sputum aspiration, the cost of applying a closed sputum aspiration tube is lower than that of an independent sputum aspiration tube, so as to reduce the expenses of patients and save consumable materials. 6.Using a closed sputum aspirator can significantly reduce the incidence of SP02 decrease during sputum aspiration Positive end-expiratory pressure (PEEP) is considered to play an important role in reducing lung exudation, atelectasis, lung injury during ventilator use, and improving oxygenation function, especially for patients with acute lung injury and acute respiratory distress syndrome. In the process of sputum aspiration with a disposable sputum aspiration tube, the airway airtightness cannot be maintained and mechanical ventilation cannot be carried out at the same time so that the positive end-expiratory pressure cannot be maintained so that the SP02 decreases in the process of sputum aspiration. Closed sputum aspiration can be carried out on patients under the condition of constantly opening the ventilator to ensure the patient's lung volume and blood oxygen saturation, avoid the reduction of lung volume and blood oxygen saturation, can better maintain the patient's oxygenation, avoid the phenomenon of reflex heart rate increase and blood pressure increase.