Utility of rapid shallow breathing index in progressive weaning of adult patients from mechanical ventilation using pressure support ventilation

Introduction: Many weaning indices have been proposed to evaluate readiness of a patient to tolerate discontinuation of mechanical ventilation. Aim: This study evaluated the utility of these indices in progressive weaning from mechanical ventilation. Methods: All patients receiving mechanical ventilation and assessed to be ready to wean clinically were included in the study. They were initially placed on pressure support, positive end expiratory pressure (PEEP) of 5-8 cm H2O and FiO2 0.4. Tidal volume, respiratory frequency, minute ventilation and rapid shallow breathing index (RSBI) were measured at baseline, 5 min, 30 min and at 2 h. The patient was also monitored for clinical signs of respiratory distress. If the patient remained stable, the pressure support was reduced by 2 cm H2O and the weaning process repeated till PSV reached 5-8 cm H2O. Results: Respiratory rate (< 35/min) and tidal volume corrected to weight (> 5 mL/kg) had high sensitivity (100% and 98.5% respectively) but lacked specificity. Minute volume of < 10 L/min lacked both sensitivity (73.1%) and specificity (50%). The RSBI (< 105 b/min/L) had very high sensitivity (99.1%), reasonable specificity (83.3%) with a positive predictive value 98.4% and a negative predictive value 90.9%. RSBI corrected to weight (7 breaths/min/mL/kg) was not useful. RSBI rate of < 20% was found to be a good weaning index even for progressive decrease in ventilatory support. Conclusion: RSBI < 105 b/min/L and RSBI rate < 20% are reliable criteria to predict success of progressive weaning from mechanical ventilation using pressure support.