Rapid shallow breathing index predicts readiness to wean?

Introduction

The rapid shallow breathing index (RSBI) has been shown to be a parameter that predicts successful weaning. A RSBI of less than 105 is a predictor for successful weaning. We investigated whether the RSBI could be a useful parameter in our patient population.

Methods

From June 2008 until March 2009 all patients who had been mechanically ventilated on our six-bed ICU were studied. Only the patients who were invasively mechanically ventilated, for longer than 6 hours, who had no missing information and did not die whilst on the ventilator were included in this study. RSBIs were measured by these patients at two different time points of weaning, firstly at the point of reduction in pressure support and then at the point of extubation. The RSBI was measured using the ventilator (Maquet servo-i) by reducing the pressure support level to zero and adjusting the PEEP to 5 cmH₂O. A significance level <0.05 was considered significant. The nonparametric Kruskall-Wallis test was used to analyse the collected data.

Results

One hundred and nineteen patients were ventilated over this time period: 74 patients did not meet the inclusion criteria; 45 were included. At the time point of further reduction in pressure support, the RSBI showed significant differences (P = 0.038) between the group who was ready for weaning and the group who was not ready for weaning. In the group with successful reduction of PS (n = 28) the RSBI was 83.54 ± 32.12, and in the group without successful reduction of PS (n = 2) the RSBI was 158.50 ± 38.89. At the point of extubation the RSBI was significant in predicting successful extubation (P < 0.001). In the group who was successfully extubated (n = 24) the RSBI was 75.25 ± 21.62, and in the group who was unsuccessfully extubated (n = 5) the RSBI was 155.20 ± 25.23.

Conclusions

At the moment of extubation, the RSBI showed significant low values in the successful group. This was also for the time point further reduction in pressure support level.