What is the Optimal Cutoff Point of Rapid Shallow Breathing Index Calculated by the Mechanical Ventilator Parameters? A Retrospective Observational Study

Background: The discontinuance of mechanical ventilatory support (MVS) is identified as weaning and weaning process is started whenever escalating factor for respiratory failure resolves. Although all weaning criteria were fulfilled, 20% of weaning attempts were unsuccessful. The Rapid Shallow Breathing Index is one of the most studied indices. In this study, we aimed to find out the optimal cutoff point of the RSBI measured in MVS. Methods: This retrospective, non-interventional cohort study was conducted at a tertiary care hospital in Ankara, Türkiye. After collecting all data, the study population was divided into two group according to weaning failure (WF). Statistical analysis included Mann Whitney U-test, Youden index, and ROC-curves to predict WF. Results: 46 patients fulfilled the inclusion criteria, and nine patients could not tolerate extubation and required reintubation [WF (+)group, 19.5%] within 72 hours. Not only the RSBI but also the other parameters like Static compliance (Cstat) and PaO2/FiO2 differed among groups. In this study, the discriminative power which was appraised using the AUC was high enough with RSBI (AUC= 0.962). Conclusion: MVS may decrease RSBI and lower predictive value in classical original cutoff point (105). However, the discriminative power with 40 as the threshold level was proven to be effective in our study.