Diaphragmatic ultrasound as a predictor of successful extubation from mechanical ventilation: thickness, displacement, or both?
Background: Best predictor of successful extubation after mechanical ventilation is a matter of debate. Objective: The aim of this study was to assess whether the degree of diaphragm thickening and/or diaphragm displacement (DD) as measured by means of ultrasound during a weaning trial can predict extubation outcomes. Methods: Thirty patients who were planned for weaning after being intubated and mechanically ventilated were prospectively enrolled in the study between January and June 2015. The rapid shallow breathing index (RSBI) was subsequently calculated, and diaphragmatic ultrasound was then carried out to assess DD and diaphragm thickening during tidal inspiration. The primary outcome was extubation success or failure. Results: Of the 30 patients included in the study, 15 were male. The mean age of patients was 59.17+13.17 years. The median duration of intubation before weaning was 4 days. There was a significant difference between mean inspiratory and expiratory diaphragmatic thickness (TDI) (t=9.66, P<0.001) An receiver operating characteristic curve was constructed for the end inspiratory TDI, end expiratory TDI, delta TDI, DD, and RSBI. The RSBI performed better than all other parameters, with an area under the curve of 0.968. A cut off value of 73.5 had 87% sensitivity and 100% specificity for predicting extubation success. All other parameters had an area under the curve less than 0.7. (0.559, 0.624, 0.655, and 0.512 for end inspiratory TDI, end expiratory TDI, delta TDI, and diaphragmatic displacement, respectively) Conclusion: Sonographically measured TDI performed better than displacement in predicting value for weaning outcome. In a respiratory ICU, however, the RSBI seems to be a more reliable and accurate tool for the purpose and should be considered in every weaning protocol. Whether TDI can be evaluated using low frequency ultrasound probes needs to be validated by further studies.