To Assess the Utility of Diaphragmatic Ultrasonography in Determining Weaning Outcome in Mechanically Ventilated Patients – A Prospective Observational Study

INTRODUCTION: Weaning of patients from ventilator is an elaborate process and takes 40–45% of the time on mechanical ventilation. Weaning failure can lead to prolonged ICU stay and increased morbidity. The prevalence of weaning failure is 18–20% in the ICU.(1,2) Diaphragmatic dysfunction can lead to weaning failure which cannot be identified by the traditional weaning index Rapid Shallow breathing Index (RSBI). Diaphragmatic ultrasonography is a non-invasive method of assessing diaphragmatic function in mechanically ventilated patients.(3) It can be used to predict weaning outcome in ventilated patients. Diaphragmatic Rapid Shallow Breathing Index (D-RSBI) is a new index in which Tidal volume (VT) in calculating Rapid Shallow Breathing Index (RSBI) is replaced by the diaphragmatic displacement (RR/DD).(4,5) Our prospective observational study was proposed to assess the utility of diaphragmatic ultrasonography in determining weaning outcome in mechanically ventilated patients. OBJECTIVES: The primary objective of our study was to assess the utility of Diaphragmatic rapid shallow breathing index (D-RSBI) in determining weaning outcomes in mechanically ventilated patients. The secondary Objective was to compare D-RSBI and Diaphragmatic Thickness Fraction (DTF) in determining weaning outcomes in mechanically ventilated patients. MATERIALS AND METHODS: Patients who were mechanically ventilated for more than 24 hours in the ICU and who were ready for the first spontaneous breathing trial (SBT) were enrolled for the study. Ethical clearance was obtained from the Institutional ethical committee before the commencement of the study. Voluntary informed consent was obtained from the relative or legally authorised representative of the patient. A GE Logiq portable ultrasonography machine with a linear and curvilinear probe was used for evaluating diaphragmatic parameters at the end of 30 minutes of SBT. RSBI, D-RSBI, DTF and Diaphragmatic displacement (DD) were calculated and their ability to predict weaning outcome were evaluated. The outcome groups were classified into simple weaning (SW) and Complicated weaning groups (CW) for study purpose. RESULTS: A total of 52 patients were included in the study as per inclusion and exclusion criteria. In the present study, a comparison of the area under the curve (AUCROC) for various parameters in predicting weaning among mechanically ventilated subjects revealed that D-RSBI had the highest predictive value, with an AUC of 0.960. At the threshold of D-RSBI ≥ 1.68, the sensitivity was 100.00% (95% CI: 73.5–100.0) and the specificity was 82.50% (95% CI: 67.2–92.7), with a positive predictive value (+PV) of 63.2% and a negative predictive value (-PV) of 100.0%. There was a strong positive correlation between D-RSBI and RSBI, and strong negative correlation between D-RSBI and DTF in predicting weaning outcome. CONCLUSION: We came to the conclusion that D-RSBI is a better predictor of weaning outcome in mechanically ventilated patients compared to RSBI, DTF and DD. Diaphragmatic ultrasonography can be routinely used in mechanically ventilated patients to determine weaning outcome as it is non- invasive and can be easily performed by adequately trained intensivists.