RESUMEN
Objective: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.Methods: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.Results: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 (cmH 2O, 1 cmH 2O = 0.098 kPa): 2.84 (-1.80, 5.83) vs. -0.94 (-8.50, 2.06), PTPes (cmH 2O·s·min -1): 1.87 (-2.50, 5.93) vs. -0.95 (-9.71, 2.56), PTPdi/PTPes ratio: 0.07 (-1.74, 1.65) vs. -1.82 (-4.15, -1.25), Pes/Pdi ratio: 0.17 (-0.43, 0.64) vs. -0.47 (-0.65, -0.11), Te (s): 1.65 (1.36, 2.18) vs. 1.33 (1.05, 1.75), all P < 0.05], there were no significant differences in Pga, Pdi, Pdimax, Pdi/Pdimax ratio, PTPga, PTPdi, EMGdi, EMGdimax, Ti and Ttot between the T-piece group and the low-level assisted pressure ventilation group [Pga (cmH 2O): 6.96 (3.54,7.60) vs. 7.74 (4.37, 11.30), Pdi (cmH 2O): 9.24 (4.58, 17.31) vs. 6.18 (2.98, 11.96), Pdimax (cmH 2O): 47.20 (20.60, 52.30) vs. 29.95 (21.50, 47.20), Pdi/Pdimax ratio: 0.25 (0.01, 0.34) vs. 0.25 (0.12, 0.41), PTPga (cmH 2O·s·min -1): 7.20 (2.54, 9.97) vs. 7.97 (5.74, 13.07), PTPdi (cmH 2O·s·min -1): 12.15 (2.95, 19.86) vs. 6.87 (2.50, 12.63), EMGdi (μV): 0.05 (0.03, 0.07) vs. 0.04 (0.02, 0.06), EMGdimax (μV): 0.07 (0.05, 0.09) vs. 0.07 (0.04, 0.09), Ti (s): 1.20 (0.95, 1.33) vs. 1.07 (0.95, 1.33), Ttot (s): 2.59 (2.22, 3.09) vs. 2.77 (2.35, 3.24), all P > 0.05]. Conclusions:When 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.