Introduction Weaning indices such as the rapid shallow breathing index (RSBI) have been used to identify mechanically ventilated patients who may be considered for spontaneous breathing trial (SBT). Traditionally, the RSBI is measured on a T-piece off any ventilatory support which requires a change in equipment and extra work for the respiratory therapist.
Hypothesis A RSBI obtained after five minutes on low level of pressure support ventilation would predict the outcome of a 120-minute SBT.
Methods We prospectively evaluated 25 mechanically ventilated medical ICU patients who were deemed ready to begin weaning by objective criteria. A SBT was initiated on pressure support ventilation (PSV) of 7 cm H2O. If the SBT was tolerated for 5 minutes, a RSBI was measured. The SBT was continued for 120 minutes unless the patient exhibited clinical signs of poor tolerance (by predefined criteria). Patients who failed the trial were returned to their previous ventilatory mode. Those who successfully finished the trial were extubated after remeasuring the RSBI. Successful extubation was defined when reintubation was not required within 48 hours.
Results 32 weaning trials were evaluated in 27 patients. 3 trials resulted in self-extubation and were excluded from analysis. 24 of the 29 trials successfully completed a 120-minute SBT, of which 22 were extubated. A RSBI at 5 minutes of < 75 had a sensitivity of 95.8%, a specificity of 60%, a positive predictive value of 92%, and a negative predictive value of 75% for accurately predicting the outcome of the 120-minute SBT. Of the 22 patients extubated, only 3 required reintubation within 48 hours.
Conclusions The RSBI done after 5 minutes on low-level PSV is an accurate, rapid predictor of the outcome of a 120-minute SBT and a patient's ability to tolerate extubation.