VAP refers to pulmonary infectious inflammation after 48 hours of invasive mechanical ventilation, which is one of the most common nosocomial infectious diseases in patients with mechanical ventilation in intensive care unit (ICU) 3. Relevant epidemiological studies show that the main pathogenic bacteria of VAP are Gram-negative bacilli, with serious mixed infection and serious drug resistance. The incidence rate is 4.5 cases/1000 mechanical ventilation days, and the mortality rate is as high as 45% in 28 days4, 5. How to effectively prevent VAP has become one of the most concerned issues in the field of critical care medicine. At present, the important measure to prevent VAP by non-pharmacological methods in clinic is to prevent cross infection, and endotracheal sputum aspiration is the main way to cause cross infection in patients with mechanical ventilation6. Therefore, the use of appropriate sputum suction device can effectively reduce the occurrence of VAP.
Patients with mechanical ventilation have more airway secretions due to long-term bed rest, decreased immune function, poor ciliary activity and hyperplasia of bronchial wall glands. Therefore, it is necessary to suck sputum regularly to remove secretions, keep respiratory tract unobstructed and prevent lung infection. According to whether it is necessary to disconnect the connection between the respiratory circuit tube and the patient's endotracheal intubation during sputum suction, the sputum suction methods are divided into open and closed7. Using traditional open sputum suction, It is easy to induce patients to have jet cough, and the sputum of patients and secretions containing a large number of pathogenic bacteria in respiratory circuit tubes will splash out, and the splashing speed may be as high as 300km/h, which will cause the environment several meters away around the air inlet and the surrounding operators and equipment to be polluted, resulting in cross-infection of patients and medical staff, and aggravating the spread of VAP. At the same time, open sputum aspiration needs to disconnect the respiratory circuit, which may lead to temporary interruption of ventilation and oxygen supply, and easily lead to sudden drop of airway pressure and reduction of lung volume, resulting in decrease of blood oxygen saturation8. Compared with open sputum suction, closed sputum suction device can effectively improve oxygen saturation, reduce clinical signs of hypoxemia, maintain positive end-expiratory pressure, reduce lung volume loss, and prevent environment, medical staff and pollution. Hamishekar found that the incidence of VAP in closed sputum aspiration was 12%, which was lower than that in open sputum aspiration (20%)9. With the clinical application of closed sputum suction device, its defects are also revealed. The sputum suction tube of the closed sputum suction system is a non-disposable item. After use, the sputum suction tube is not washed clean, and the sputum adheres to the inner and outer walls of the sputum suction tube, which leads to the propagation of pathogenic bacteria on the tube wall. Because it is difficult to replace, it falls off in the airway when sucking sputum again, resulting in secondary pollution of the airway. In addition, after many times of sputum suction by the closed sputum suction device, the soft catheter sheath will be twisted, which will shorten its length. The shortened catheter sheath prevents the catheter from completely withdrawing from the trachea, thus increasing the airway resistance and leading to some ventilator-related complications10. Moreover, although the closed sputum suction device tends to reduce the occurrence of VAP, the cost is high, which greatly increases the economic burden of patients11.
In order to overcome the defects of the above-mentioned sputum suction device, we have continuously explored it and developed a new type of medical protective breathing circuit tube, which can not only prevent sputum splashing, but also use disposable sputum suction tube, and has independent intellectual property rights (China National Invention Patent No. ZL 2019 1 0141806.5; China National Utility Model Patent No. ZL 2019 20241720.5). Compared with the common respiratory circuit, this new medical protective respiratory circuit has the following advantages: (1) It can effectively reduce cross-infection, avoid the exposure of patients' respiratory tract and effectively reduce the occurrence of VAP; (2) It can prevent sputum and secretion containing pathogenic bacteria from splashing, effectively protect medical staff and ICU environment, improve the safety of nursing work and reduce the nosocomial infection rate; (3) It is convenient for the operation examination of fiberoptic bronchoscope, and at the same time, it plays a very good protective role for the operator; (4) The price is cheap, which can reduce the medical expenses of patients and is convenient for clinical application.
To sum up, the medical protective respiratory circuit designed by us has simple structure, low cost and convenient use, which can not only effectively protect medical staff and ICU environment, but also control the cross infection of pathogenic bacteria and reduce the occurrence of VAP. Therefore, it has a good prospect of clinical application and popularization.