Predictive Value Of Cardiac And Diaphragmatic Ultrasound Combined With Serum NT-proBNP For Ventilator Evacuation

Background: Transthoracic echocardiography(TTE)is the primary noninvasive imaging modality for quantitative and qualitative evaluation of cardiac anatomy and function,which arouse the intensive interests of clinicians in the prediction of successful weaning from invasive mechanical ventilation of respiratory failure patients.Objective:To evaluate the predictive value of TTE,diaphragmatic excursion(DE)and serum N-terminal pro-B-type natriuretic peptide(NT-proBNP)in the weaning of invasive mechanical ventilation in patients with respiratory failure.Methods: Thirty-six cases with invasive mechanical ventilation were divided into success group(n=28)and failure group(n=8)according to whether reintubation was needed within the following 48 hours.The ratio of mitral inflow velocity(E)to mitral annulus velocity(e')and DE before and after spontaneous breathing test(SBT)were observed by Doppler ultrasound image.Additionally,the serum NT-proBNP at admission and at the end of SBT in both groups were measured.Receiver operating characteristic curve(ROC)was used to determinate the optimal cut-off value of all the indexes by calculating the area under the ROC curve(AUC).Results: Of all the 36 cases included,28 were successfully extubated(success group,n=28)and 8 failed to wean(failure group,n=8).Serum NT-proBNP at the end of SBT was significantly higher in the failure group than that in the success group(p=0.004).Compared with the success group,the ratio of E/e'value after SBT was significantly higher in the failure group(p=0.001).The AUC value of E/e' after SBT was 0.799 with a cut-off value of 12.63 showed the highest diagnostic efficiency with better sensitivity(75%)and specificity(85.7%).The value DE after SBT in the success group was significantly higher than that of the failuregroup(p=0.001).The AUC of DE after SBT was 0.812 with a cutoff value of 11.3mm showed the highest diagnostic efficiency with better sensitivity(92.9%)and specificity(62.5%).When combined,The AUC of E/e' value,DE and NT-proBNP was 0.862(95% confidence interval 0.715-1.000,p=0.002)with a sensitivity and specificity of 75% and 92.9% respectively.Conclusion:TTE is helpful in identifying high-risk patients with Cardiac-related failure of weaning from mechanical ventilation,and ultrasound detection of DE can add to predictive value of TTE in successful weaning.Meanwhile,serum NT-proBNP showed its usefulness in ventilator weaning,especially combined with the other two predictive indexes.