• Bo Zhang and Ying-zhi Qin.
• Intensive Care Unit, Tianjin Third Hospital, Tianjin 300170, China.
• Zhongguo Wei Zhong Bing Ji Jiu Yi Xue. 2009 Jul 1;21(7):397-401.

ObjectiveTo determine the threshold value of rapid-shallow-breathing index (RSBI) and its increased percentage (Delta RSBI) as predictors for successful weaning in spontaneous breathing trial (SBT) with pressure support ventilation (PSV) and T-piece.MethodsIn 2007, there were 208 patients on ventilators with oral intubation. They were divided into two groups: the PSV group (93 patients) and the T-piece group (115 patients). The duration of SBT was 30 minutes. Weaning indexes [mouth occlusion pressure 0.1 (P0.1), breathing rate (f), tidal volume (V(T))] of SBT 3 minutes and 30 minutes were recorded in each group. The averages of RSBI and Delta RSBI were calculated and compared between two groups.ResultsAmong 208 patients, in 168 patients weaning was successful and the ratio was 80.77%. The successful ratios of PSV and T-piece group were 83.87% and 78.26%, respectively (P > 0.05). In PSV and T-piece groups the average of RSBI value (SBT 30 minutes) was (67.18+/-11.55) breaths x min(-1) x L(-1) and (99.11+/-15.53) breaths x min(-1) x L(-1), respectively (P < 0.01); the average of Delta RSBI was (69+/-33)% and (119+/-35)% (P < 0.01). In PSV group, the area under receiver operating characteristic (ROC) curve of RSBI was 0.747+/-0.045 (P = 0.000); when RSBI =75 breaths x min(-1) x L(-1), the diagnostic accuracy was 87%; the area under ROC curve of Delta RSBI was 0.709+/-0.065 (P = 0.001), and when Delta RSBI=90%, the diagnostic accuracy was 82%. In T-piece group, the area under ROC curve of RSBI was 0.821+/-0.049 (P = 0.000); when RSBI =100 breaths x min(-1) x L(-1), the diagnostic accuracy was 82%; the area under ROC curve of Delta RSBI was 0.738+/-0.046 (P = 0.000); when Delta RSBI =130%, the diagnostic accuracy was 77%.ConclusionThe average values of RSBI (SBT 30 minutes) are significantly different between the two groups. In PSV and T-piece groups, using RSBI = 75 breaths x min(-1) x L(-1) and 100 breaths x min(-1) x L(-1) as the threshold value for predicting successful weaning is more valuable than other values. Sequential observation of Delta RSBI is also valuable in predicting a successful extubation.

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