| Objective To determine the significance and threshold value of rapid-shallow-breathing index(RSBI)and its increased percent(ΔRSBI)as predictors for successfully weaning in spontaneous breathing trial(SBT)with pressure support ventilation(PSV)and T-piece.Methods In 2007,There were 208 patients on ventilators in 1-28 days with oral intubation.Based on SBT with PSV or T-piece,208 patients were divided into two groups:the PSV group and the T-piece group.The duration of SBT was 30min.Record weaning indexes[mouth occlusion pressure 0.1(P0.1),tidal volume(Vt),breathing rate(f)]of SBT3min and 30min in each group. Calculated and compared the average of RSBI(SBT3min and 30min,RSBI=f/Vt)andΔRSBI(ΔRSBI=[RSBI(30min)-RSBI(3min)]/RSBI(3min)×100%)in each group.Use the receiver operating characteristic(ROC)curve to analyze and determine the sensitivity,specificity and the threshold value of RSBI andΔRSBI as predictors for successfully weaning.Results 208 patients included 117 male and 91 female patients.The age was 20-94 years old and average was 71.28+/-11.47 years old.63 patients were after surgery operations and 145 patients were not.The duration of ventilation was 1-28 days,the average was 4.68+/-3.73 days.168 patients were successfully weaning from ventilator and 40 patients were failed.The achievement ratio of ventilator weaning is 80.77%.The PSV group had 93 patients and the T-piece group had 115 patients.The average of age,ratio of male and female,duration of ventilation were not significant different between the two groups.The achievement ratio of PSV group and T-piece group were 83.87%and 78.26%,(P=0.307),the different between the two groups was not significant.In PSV group,the average of RSBI(SBT30min)was 67.18+/-11.55(breaths/min·L);In T-piece group,the average of RSBI(SBT30min)was 99.11+/-15.53(breaths/min·L),(P=0.000).The different was significant between the two groups.In PSV group,the average ofΔRSBI was 69+/-33%;In T-piece group,the average ofΔRSBI was 119+/-35%,(P=0.000).The different was significant between the two groups.In PSV group,the area of ROC curve of RSBI was 0.747+/-0.045,the 95%confidence interval was 0.658-0.835, (P=0.000);using RSBI=75(breaths/min·L)as the threshold value for predicting successful weaning,the sensitivity,specificity,positive predictive value,negative predictive value and diagnostic accuracy were 0.919,0.571,0.923,0.600 and 87% respectively;the area of ROC curve of ARSBI was 0.709+/-0.065,the 95% confidence interval was 0.582-0.835,(P=0.001),using ARSBI=90%as the threshold value for predicting successful weaning,the sensitivity,specificity,positive predictive value,negative predictive value and diagnostic accuracy were 0.865,0.536,0.905,0.421 and 82%respectively.In T-piece group,the area of ROC curve of RSBI was 0.821+/-0.049,the 95%confidence interval was 0.725-0.916, (P=0.000);using RSBI=100(breaths/min·L)as the threshold value for predicting successful weaning,the sensitivity,specificity,positive predictive value,negative predictive value and diagnostic accuracy were 0.833,0.781,0.924,0.558 and 82% respectively;the area of ROC curve of ARSBI was 0.738+/-0.046,the 95% confidence interval was 0.648-0.829,(P=0.000),usingΔRSBI=130%as the threshold value for predicting successful weaning,the sensitivity,specificity,positive predictive value,negative predictive value and diagnostic accuracy were 0.833,0.560,0.872,0.483 and 77%.Conclusions The average of RSBI(SBT30min) of T-piece Group was significant higher than PSV group.In PSV group,using RSBI=75(breaths/min·L)as the threshold value for predicting successful weaning was better than other values.In T-piece Group,the threshold value was RSBI=100(breaths/min·L).In the duration of SBT,to continual observe the increased percent of RSBI(ΔRSBI)was important in predicting successful weaning,too.In PSV group,at the end of SBT,when theΔRSBI≤90%the prognosis of weaning was better. In T-piece group,at the end of SBT,when theΔRSBI≤130%the prognosis of weaning was better.
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