Assessment of the rapid shallow breathing index as a predictor of weaning of patients with prolonged mechanical ventilation

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