Does diaphragm ultrasound improve the rapid shallow breathing index accuracy for predicting the success of weaning from mechanical ventilation?

Abstract

BACKGROUND\nThis prospective study investigated whether taking into account diaphragmatic excursion (DE) measured by ultrasonography would improve the performance of the rapid shallow breathing index (RSBI) to predict extubation success or failure.\n\n\nOBJECTIVES\nThe aim of the study was to compare the new composite index named the rapid shallow diaphragmatic index (RSDI), and the RSBI measured during a spontaneous breathing trial regarding their ability to predict the need for re-intubation at 72 h.\n\n\nMETHODS\nOne hundred mechanically ventilated patients underwent daily 30-min spontaneous breathing trials (SBTs) under pressure support ventilation of 6\xa0cm\xa0H2O and end-expiratory pressure of 0\xa0cm\xa0H2O until the SBT was considered successful and followed by extubation. The performances of RSBI (respiratory rate/tidal volume) and of the ratio RSBI/DE measured at 5 and 25\xa0min of the successful SBT\xa0were compared in terms of area under the receiver operating characteristics curve (AUC), for predicting extubation success at 72\xa0h. As secondary analysis, extubation and weaning success at 7 d\xa0were also considered. As exploratory analyses, predictive indices incorporating both clinical characteristics, the DE, and ultrasound diaphragm thickening fraction (DTF) were investigated.\n\n\nRESULTS\nRSBI and RSBI/DE showed AUCs with 95% confidence intervals consistently extending below 0.50, either at the 5th (0.55 [0.36-0.74] and 0.55 [0.34-0.75], respectively) or at the 25th minute of SBT (0.49 [0.27-0.71] and 0.50 [0.29-0.68], respectively) for predicting weaning success at 72\xa0h\xa0or at 7 d\xa0(5th min: 0.53 [0.37-0.70] and 0.54 [0.37-0.70], respectively; 25th min: 0.54 [0.37-0.71] and 0.55 [0.39-0.71], respectively). An exploratory index incorporating the accessory respiratory muscle activity, DE, DTF, and respiratory rate at 5th min of SBT\xa0showed AUCs for predicting extubation success at 7 d\xa0in the 78 patients with DTF measurement (0.77 [0.64-0.90])\xa0that were significantly higher than that of the RSBI (P\xa0=\xa00.017) and RSBI/DE (P\xa0<\xa00.001) in the same respective populations.\n\n\nCONCLUSIONS\nThe RSBI and the ratio RSBI/DE failed to predict weaning success when measured during an SBT performed under minimal pressure support. Predictive indices incorporating ultrasound DE and DTF may merit further investigation.