Weaning Of Mechanically Ventilated Patients Guided By Assessment Of Lung Tidal Distribution

Objective:To evaluate the predictive value of GI,SDRVD,?EELI/vt,SDRC and ITGD in outcome of weaning of mechanically ventilated patients.Methods:An observational clinical research was conducted.Patients admitted to the Department of Critical Care Medicince,Zhongda Hospital,Southeast University from May 2017 to December 2017,and who had pass the screening deemed ready for a SBT were enrolled.The protocol started with patients ventilated on a PSVof 8 cm H₂O above a PEEP of 5 cm H₂O for 30minutes.Then assist was removed,and a 30 minute SBT（T-piece trial）was performed.The data were recorded at inclusion during the trial:（1）Characteristics of the patients’main demographics（name,age,gender,diagnosis,check in time,APACHE II score,SOFA score and so on）.（2）Arterial blood gas analysis（pHa,PaCO₂,PaO₂,PaO₂/FiO₂）at 5 min before SBT and the end of SBT（30 min of SBT or the time of SBT failed）,respectively;（3）Heart rate（HR）and Mean arterial pressure（MAP）at 5 min before SBT and 0,5,15,and 30 min of SBT,respectively.（4）Tidal volume（vt）and breathing frequency（f）at 5min before SBT;（5）EIT recordings were performed at5min before SBT and during SBT.Patients who resumed mechanical ventilation during SBT,or required noninvasive ventilation（NIV）after extubation,or were reintubated,or deceased within 48hours after extubation were considered to have failed extubation.According to the outcome of weaning,the patients were divided into two groups:weaning success and weaning failure.Comparing the differences of GI,SDRVD,?EELI/vt,SDRC,and ITGD before and during SBT between the two groups,and the predictive value of those indices with regard to the outcome of weaning were analyzed.Results:1.Baseline Characteristics37 patients were enrolled,and 24 were successfully extubated,for 13,extubation failed.There was no difference in:age,APACHEII score,SOFA score,duration of mechanical ventilation,HR,MAP and arterial blood gas analysis between successfully weaned group and failed weaned group（P>0.05）.2.Comparison of hemodynamics and arterial blood gas analysis in successfully weaned group and failed weaned group during SBTThere was no significant difference in HR and MAP between successfully weaned group and failed weaned group during SBT（P>0.05）.At the end of SBT,there was no significant difference in arterial blood gas analysis between the two groups（P>0.05）.3.The predictive value of GI for weaning failure at 5 min before SBT and during SBTThe GI of the successfully weaned group at 5 min before SBT,0 min,5 min,15 min,and 30min of SBT were 0.46±0.16,0.49±0.17,0.48±0.17,0.48±0.17and 0.49±0.15,respectively;of the weaning failure group were 0.63±0.22,0.79±0.28,0.79±0.29,0.84±0.41 and 0.89±0.50,respectively.Patients in the group that failed weaned had significantly higher GI before and during SBT compared to the group that was successfully weaned（P<0.05）.GI value of>0.62 before SBT had a sensitivity of 0.54 and specificity of 0.92 for predicting weaning failure（AUC=0.763）.The GI predicted a failed weaning had an AUC of 0.854,a sensitivity of 0.92,and a specificity of 0.75 with the optimal threshold of>0.52 at 0 min of SBT.GI value of>0.50 at 5min of SBT predicted failed weaning with a sensitivity of 1.00 and a specificity of 0.67（AUC=0.865）.The AUC of GI at15min of SBT to predict weaning failure was 0.881,1.00 for sensitivity,and 0.75 for specificity with a cutoff value of>0.52.Assuming a GI cutoff value of>0.52,sensitivity of 1.00 and specificity of 0.67 were reached for predicting a failed weaning at 30 min of SBT（AUC=0.877）.4.The predictive value of SDRVD for weaning failure at 5 min before SBT and during SBTThe SDRVD values of the successfully weaned group at 5 min before SBT,0 min,5 min,15min,and 30 min of SBT were 7.88±5.48,11.13±4.96,11.32±4.45,11.13±5.22 and 11.72±5.14,respectively;of the weaning failure group were 12.82±5.72,16.63±5.60,16.87±5.40,17.26±7.24and 19.01±7.21,respectively.The SDRVD values in the failed weaned group at 5min before SBT and during SBT were significantly higher than those in the successfully weaned group（P<0.05）.The SDRVD before SBT predicting failed weaning presented an AUC of 0.756,a sensitivity of 0.85,and a specificity of 0.70 with the optimal threshold of>7.7.The SDRVD of>14.25 predicted a failed weaning had a sensitivity of 0.70 and a specificity of 0.75 at 0 min of SBT（AUC=0.760）.SDRVD value of>15.45 at 5min of SBT predicted failed weaning with a sensitivity of 0.70 and a specificity of 0.83（AUC=0.780）.The AUC of SDRVD at 15min of SBT to predict weaning failure was 0.748,0.69 for sensitivity,and 0.79 for specificity with a cutoff value>15.35.Assuming a SDRVD cutoff value of>15.60,sensitivity of 0.85 and specificity of 0.69 were reached for predicting a failed weaning at 30 min of SBT（AUC=0.788）.5.The predictive value of Mean?EELI/vt for weaning failure during SBTThe Mean?EELI/vt value was-0.61±0.54 in the successful group at 0 min of SBT,and in the failed group was-1.05±0.55（P<0.05）.There was no significant difference of the Mean?EELI/vt values between the two groups at 5 min,15 min,and 30 min of SBT.Mean?EELI/vt of<-0.92 at0min of SBT predicted failed weaning with a sensitivity of 0.83 and a specificity of 0.54（AUC=0.739）.6.The predictive value of ITGD for weaning success at 5 min before SBT and during SBTFour different patterns of regional ITGD were found.Typical ventral（non-dependent）and dorsal（dependent）ITGD during inspiration was plotted as pattern 1（progressively homogeneous）,which had a higher weaning success rate（21 of 28 patients succeed,P<0.05）.Patterns 2,3 and 4were found in 3（1 patient succeed）,2（1 patient succeed）and 4（1 patient succeed）of 37 patients,respectively.The pattern 1 predicted a successful weaning had a sensitivity of 0.88 and a specificity of 0.46 before and during SBT.7.The predictive value of SDRC for weaning failure at 5 min before SBT and during SBTSDRC values were higher in patients who had failed to wean compared with patients who had successfully weaned at 5min before SBT,0min,5min,15min,and 30min of SBT,but there was no significant difference（P>0.05）.8.The predictive value of f/vt for weaning failure at 5 min before SBTf/vt of weaning failure group was higher than the successful group at 5min before SBT（67.09±28.41vs.45.18±14.27,p=0.005）,which predicting failed weaning presented an AUC of 0.718,a sensitivity of 0.59,and a specificity of 0.85 with the optimal threshold of>60.64 breaths/min.L.Conclusions:The GI,SDRVD,Mean?EELI/vt and ITGD have predictive value regarding the outcome of weaning of mechanically ventilated patients.