[Comparison among three methods to measure the rapid shallow breathing index in patients submitted to weaning from mechanical ventilation].

BACKGROUND AND OBJECTIVES: To compare the attainment of the rapid shallow breathing index (IRRS) in modalities PSV 10 cmH2O and PEEP 5 cmH2O (PSV10), CPAP 5 cmH2O (CPAP5) and spontaneous breathing (SB), correlating them with success on failure in the withdrawal of mechanical ventilation (MV).

METHODS: Prospective study including 54 patients in MV > 48 hours, submitted to the IRRS in three ventilatory modalities: PSV10, CPAP5 and SB at the moments before and after T-tube spontaneous breathing. The patients were removed from MV when IRRS was < 105.

RESULTS: There wasn't statistically significant difference between IRRS values at the moments before and after T-tube SB. There was statistically significant difference IRRS value between the modalities CPAP5 and PSV10 (p = 0.008), and between the modalities SB and PSV10 (p = 0.01) at the moment before T-Tube SB and of IRRS value, gotten between CPAP5 and PSV10 (p = 0.01) at the moment after T-tube SB.

CONCLUSIONS: From this sample, it can be observed that IRRS values are overestimated when gotten in modality PSV10. It was also evidenced that there is no need of a 30 min T-tube SB before extubation, when the weaning is performed with the technique of gradual reduction of PSV. This study suggested that IRRS is able to predict weaning success; however it is not able to determine failure when it was < 105. It is recommended that IRRS must be analyzed in association with other predictive weaning parameters.