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To compare the difference of low-level assisted ventilation and T-piece method on respiratory mechanics of patients with invasive mechanical ventilation during spontaneous breathing trial (SBT) within 3 days before extubation.A retrospective observational study was conducted. Twenty-five patients with difficulty in weaning or delayed weaning from invasive mechanical ventilation who were admitted to department of critical care medicine of the First Affiliated Hospital of Guangzhou Medical University from December 2018 to June 2020, and were in stable condition and entered the weaning stage after more than 72 hours of invasive mechanical ventilation were studied. A total of 119 cases of respiratory mechanical indexes were collected, which were divided into the low-level assisted ventilation group and the T-piece group according to the ventilator method and parameters used during the data collection. The different ventilation modes related respiratory mechanics indexes such as the esophageal pressure (Pes), the gastric pressure (Pga), the transdiaphragmatic pressure (Pdi), the maximum Pdi (Pdimax), Pdi/Pdimax ratio, the esophageal pressure-time product (PTPes), the gastric pressure-time product (PTPga), the transdiaphragmatic pressure-time product (PTPdi), the diaphragmatic electromyography (EMGdi), the maximum diaphragmatic electromyography (EMGdimax), PTPdi/PTPes ratio, Pes/Pdi ratio, the inspiratory time (Ti), the expiratory time (Te) and the total time respiratory cycle (Ttot) at the end of monitoring were recorded and compared between the two groups.Compared with the T-piece group, Pes, PTPes, PTPdi/PTPes ratio, Pes/Pdi ratio and Te were higher in low-level assisted ventilation group [Pes (cmHWhen mechanically ventilated patients undergo SBT, the use of T-piece method increases the work of breathing compared with low-level assisted ventilation method. Therefore, long-term use of T-piece should be avoided during SBT.

To understand the function of diaphragm and analyze the clinical factors affecting the function of diaphragm by measuring twitch tracheal pressure (TwPtr) in patients with mechanical ventilation and in the weaning phase.Patients with more than 48 hours of invasive mechanical ventilation admitted to the department of critical care medicine of the First Affiliated Hospital of Guangzhou Medical University from December 2015 to March 2017 were enrolled. After the patient entered the weaning stage, TwPtr of patients was monitored by two-way non repetitive automatic respiratory trigger device, the effects of duration of mechanical ventilation, severe pulmonary infection, sedative application and chronic obstructive pulmonary disease (COPD) on weaning were analyzed.A total of 62 patients were included, of which 45 were male and 17 were female. The average age was (66.8±11.7) years old. Twenty-three cases had severe pneumonia. The absolute value of TwPtr in severe pneumonia group was lower than that in non-severe pneumonia group [cmHFor patients in the weaning stage of mechanical ventilation, severe pulmonary infection is one of the factors that affect the diaphragm dysfunction. There is a certain correlation between the diaphragm dysfunction and the use of sedatives.

To explore the effect of prone position ventilation (PPV) on respiratory mechanics and prognosis in patients with acute respiratory distress syndrome (ARDS) concurrent with interstitial lung disease (ILD).The data of 36 severe ARDS patients admitted to Department of Critical Care Medicine of the First Affiliated Hospital of Guangzhou Medical University from February 2013 to January 2015, were retrospectively analyzed. They were then divided into two groups according to the presence of ILD or not. The changes in respiratory mechanics and oxygenation indexes were compared before and after PPV treatment in all the patients. Kaplan-Meier method was applied to draw the 60-day survival curves of both groups.There were 17 cases with ILD among these 36 severe ARDS patients. (1) No significant difference was found in baseline data between ILD group and non-ILD group. (2) Respiratory mechanics and oxygenation pre-PPV and post-PPV: compared with pre-PPV, oxygenation index (PaO2/FiO2, mmHg, 1 mmHg = 0.133 kPa) post-PPV was significantly increased in both groups [ILD group : 132.0 (93.5, 172.0) vs. 118.7 (92.0, 147.8); non-ILD group: 126.1 (100.9, 170.0) vs. 109.2 (89.0, 135.0), both P0.05]. Compared with pre-PPV, positive end-expiratory pressure (PEEP, cmH2O, 1 cmH2O = 0.098kPa) post-PPV was significantly higher in ILD group [10.0 (10.0, 12.0) vs. 10.0 (9.2, 12.0), P0.05], and respiratory rate (RR, times/min) was significantly lower in non-ILD group [24.5 (22.0, 27.0) vs. 25.5 (22.8, 28.0), P0.05]. The compliance of the respiratory system (Crs, mL/cmH2O) post-PPV in non-ILD group was significantly lower than that of the ILD group [19.7 (16.1, 28.6) vs. 23.0 (19.0, 29.7), P0.05]. (3) Respiratory mechanics and oxygenation pre-PPV and post-PPV in total: after all the PPV therapy, PaO2/FiO2 (mmHg) was significantly increased in non-ILD group [135.0 (86.0, 200.0) vs. 97.4 (69.2, 127.5), P0.05], PaO2/FiO2 after all the PPV therapy in non-ILD group was also higher than that in ILD group [135.0 (86.0, 200.0) vs. 78.7 (59.3, 114.9), P0.05]. No significant difference in Crs (mL/cmH2O) before PPV treatment was found between non-ILD and ILD groups [24.3 (15.9, 48.9) vs. 18.9 (12.7, 27.3), P0.05], and Crs was lower after PPV treatment in both groups, but without significant difference [non-ILD group: 22.7 (15.2, 27.1) vs. 24.3 (15.9, 48.9); ILD group: 16.2 (12.8, 25.6) vs. 18.9 (12.7, 27.3), both P0.05]. (4) The 60-day mortality in ILD group was significantly higher than that in non-ILD group [88.2% (15/17) vs. 57.9% (11/19), P = 0.047). It was shown by Kaplan-Meier curves that 60-day survival patients in ILD group was significantly lower than those in non-ILD group (χ2 = 5.658, P = 0.017).PPV can improve oxygenation in severe ARDS. Compared with non-ILD group, though the compliance of respiratory system in ILD group is increased during PPV, long-term effect is better in non-ILD group.