RESUMO
OBJECTIVE: To determine the respiratory indices capable of improving predictive accuracy of extubation success through serial measurements of during spontaneous breathing trial (SBT) in automatic tube compensation (ATC) pattern of mechanical ventilation. METHODS: For this prospective observational study, patients ventilated over 48 hours were enrolled according to the weaning criterion and underwent a 60 minutes spontaneous breathing trial (SBT) in ATC pattern (ATC = 100%, FiO2 = 0.4, PEEP = 0 cm H2O, PS = 0 cm H2O). During SBT, heart rate (HR) and mean artery pressure (MAP) were monitored continuously and minute volume (VE), respiratory rate (RR), tidal volume of spontaneous breath (VT), rapid shallow breathing index (RSBI), change and rate of change (ΔRSBI60_1 and ΔRSBI60_1/RSBI1, etc.) were recorded or calculated at the first, 30(th) and 60(th) minute of SBT. Patients tolerating the trial were extubated immediately. Clinical data and respiratory indices during SBT were compared between patients in extubation success group and those in extubation failure group. Predictive accuracy of extubation success was assessed by area under the receiver operating characteristic (ROC) curve (AUC) for each index. RESULTS: The duration of mechanical ventilation was longer in patients of extubation failure group than that of extubation success group (10.75 ± 2.73: 7.47 ± 5.11, P = 0.035) and extubation failure rate was 17.14%. During SBT, RSBI increased initially and then decreased in patients of extubation success group, but increased continuously in patients of extubation failure group. There were significant difference of ΔRSBI60_1 and ΔRSBI60_1/RSBI1 in patients between extubation success and failure groups (-11.5 ± 16.6: 12.1 ± 38.9, P = 0.001 and -17 ± 26: 13 ± 39, P = 0.028). AUCs of RSBI60, ΔRSBI60_1 and ΔRSBI60_1/RSBI1 were 0.75, 0.73 and 0.72 and the sensitivity, specificity and diagnostic accuracy 81.0%, 66.7% and 78.5% respectively. CONCLUSION: It is important to observe change of various respiratory indices dynamically during SBT in patients ventilated in ATC pattern. ΔRSBI60_1 and ΔRSBI60_1/RSBI1 have greater predictive value for extubation success. Stable or decreased RSBI60 means higher extubation success rate.
