Comparison of Ultrasound-based Diaphragmatic Thickness Fraction (DTF) with Rapid Shallow Breathing Index and DTF alone for Predicting Successful Weaning from Mechanical Ventilation: A Randomised Control Trial

Abstract

Introduction: The timing for weaning from mechanical ventilator support is crucial because both early discontinuation and delayed weaning may lead to increased morbidity and mortality as well as high medical cost. Diaphragmatic Thickness Fraction (DTF), among the various ultrasound-based diaphragmatic measurements, can not only assess the readiness to wean but also predict the simple weaning. The Rapid Shallow Breathing Index (RSBI) or Yang Tobin index is a tool that is used in the weaning of mechanical ventilation. RSBI is the ratio of respiratory rate to tidal volume in litre (RR/VT). Aim: To estimate success of weaning process by using the ultrasound-guided DTF% alone as a weaning predictor, and compare it with the index derived from the combination of both DTF% and RSBI. Materials and Methods: This randomised control study was conducted on 100 patients admitted to Intensive Care Unit (ICU) during one year, from October 2019 to September 2020. When the patients satisfied the weaning criteria, they were given Spontaneous Breathing Trial (SBT). After SBT the ultrasound was done and RSBI were calculated. Composite Index (CI) was derived by combining DTF% and RSBI. Patients were divided in two groups. In “group C” CI was used as weaning predictor, and in “group D” DTF% alone was taken as weaning predictor. Incidence of weaning failure was noted in each group. The statistical analysis was done using Statistical Package for the Social Sciences (SPSS) Version 19.0. Chi-square test, Student’s t-test, Receiver Operating Characteristic (ROC) curve, 2x2 tables were used. Results: The DTF% value >44.0% was found to be 95.2% sensitive, and 96.2% specific based on the ROC curve. The proportion of cases requiring reintubation was significantly higher in group D (DTF%) compared to group C (CI) (30.0% vs. 12.0%). RSBI with DTF% had a better sensitivity and specificity than DTF% alone. Conclusion: DTF% with RSBI is a much better predictor than DTF% alone. Sonography is subjective and has a long learning curve DTF% can be combined with RSBI to improve patient outcome.