Assessment of the Rapid Shallow Breathing Index as a Predictor of Weaning of Patients with Prolonged Mechanical Ventilation

Background: About 8% of patients experience prolonged mechanical ventilation after cardiac surgery. Development of criteria for successful liberation of a patient from mechanical ventilation and extubation may be highly dependent on the clinical situation. Different criteria were used for ventilator weaning. We designed a clinical trial to determine the usefulness of rapid shallow breathing index (RSBI) as a predictor for successful weaning from mechanical ventilation. Materials and Methods: In a prospective observational study, 52 patients who had prolonged mechanical ventilation ( 72 h) after open cardiac surgery were studied. Patients had 60 – min spontaneous breathing trials and satisfied at least 5 weaning predictors and fulfilled the criteria for discontinuing mechanical ventilation. Traditional weaning criteria and RSBI were determined. According to the outcome assessment of weaning, patients were divided into failure or success groups. Results: The mean RSBI values were significantly different between the failure (103.5±21.9 breath/min/L) and success groups (80.4±15.3 breath/min/L, p=0.0001). There was no significant difference regarding the values of other prediction criteria between the two groups. Using RSBI 105 (breath/min/L) as the threshold value for predicting successful weaning, sensitivity, specificity, positive predictive value ( PPV), negative predictive value ( NPV), and diagnostic accuracy were 92.5%, 70%, 92.5%, 70% and 88% respectively. Conclusion: Although a small number of patients require prolonged ventilatory support after open cardiothoracic surgeries, growing experience in critical care settings and mechanical ventilation cause favorable outcomes. Ventilator weaning is more likely to be successful if RSBI is less than 105 (breath/min/L). This index is a more valuable and accurate predictor of weaning than other weaning predictors.