[The effect of a breathing trainer on relieving airway pressure caused by active cough in patients with mechanical ventilation]

Objective: To explore the effect of a breathing trainer on relieving the peak airway pressure caused by forced exhalation at the end of deep inspiration, gentle coughing at the end of calm inspiration and forced coughing at the end of deep inspiration in patients undergoing mechanical ventilation. Methods: From July to September 2018, 15 patients undergoing mechanical ventilation were selected from the First Affiliated Hospital of Guangzhou Medical University, including 5 patients with invasive ventilation (3 with tracheotomy and 2 with endotracheal intubation), and 10 patients with non-invasive ventilation through mask. The patients included 14 males and 1 female, aging 48-79 years, with an average age of (68±10) years. A Breathing Trainer developed by both Dongguan Yongsheng Medical Products Co., Ltd. and Guangzhou Institute of Respiratory Health was used to relieve the peak airway pressure. A one-way expiratory valve connected with a spring at the expiratory end of the Breathing Trainer was not opened until the pressure inside the airway was higher than 20 cmH(2)O (1 cmH(2)O=0.098 kPa), and opened completely when the pressure was higher than 35 cmH(2)O. Both before and after the Breathing Trainer was connected to the respiratory circuit, the patients were asked to exhale hard at the end of deep inspiration, to cough gently at the end of calm inspiration and to cough forcefully at the end of deep inspiration and the airway pressure were measured respectively. Each action was tested 3 times, and the interval time of each test was 1 min, and the interval of each action was 10 min. Results: Among the patients with tracheotomy or endotracheal intubation for invasive mechanical ventilation, when the patients exhaled hard at the end of deep inspiration,coughed gently at the end of gentle inspiration and coughed forcefully at the end of deep inspiration, the peak airway pressure measured before the ventilation circuit was connected to the Breathing Trainer was (30.0±4.5), (31.4±5.0) and (34.9±5.0)cmH(2)O, respectively, which was significantly higher than that after the ventilation circuit was connected to the Breathing Trainer(26.3±2.9), (26.7±3.5) and (29.0±4.1) cmH(2)O (all P<0.01). Among the patients with non-invasive mechanical ventilation wearing face masks, when the patients exhaled hard at the end of deep inspiration, coughed gently at the end of gentle inspiration and coughed forcefully at the end of deep inspiration, the peak airway pressure was (17.7±1.9), (16.6±2.5) and (18.9±2.5) respectively, before the ventilation circuit was connected to the Breathing Trainer, and was (18.9±2.5), (16.3±1.9) and (18.8±2.0) cmH(2)O respectively, after the ventilation circuit was connected to the Breathing Trainer. There was no significant difference between them (P>0.05). Conclusion: The application of Breathing Trainer in the mechanical ventilation circuit of tracheotomy or endotracheal intubation could significantly reduce the peak airway pressure caused by hard exhalation and cough. It could be used as an active cough assist device for mechanical ventilation patients to prevent high airway pressure.