الفهرس 
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Abstract
T
horacic fluid content represents the whole (extravascular, intravascular, and intrapleural) fluid component in the thorax; thus, TFC was considered to provide an estimation of the extravascular lung water in absence of significant pleural or pericardial effusion.
Fluid Status using electrical cardiometry, ICON was shown as thoracic fluid content (TFC), stroke volume variation (SVV) and corrected flow time (FTC). TFC is derived from the thoracic electrical base impedance (1/base impedance), which is dependent on thoracic intravascular and extravascular fluid content. Larger TFC indicates a higher total thoracic fluid volume.
Thoracic fluid content showed moderate predictive ability for weaning failure; this predictive ability became excellent in the subgroup of patients with impaired systolic function. Measurement of the TFC depends on the impedance cardiography phenomenon which changes according to the resistance of thoracic contents to electric current.
The presence of lung congestion is an important cause for weaning failure especially in cardiac patients. Lung congestion may also be triggered by the spontaneous breathing trial due to the increase in the left ventricular afterload, as well as the increase in the venous return and the subsequent increase in the cardiac preload. The TFC is an index for both extra and intra-vascular thoracic fluid; however, the TFC showed good correlation with ultrasound in estimation of extravascular lung water Therefore, high TFC value could be an indirect measure of lung congestion and/or hypervolemia which is a known risk factor for failed weaning.
So, this study aimed to assess TFC as a novel parameter for prediction of successful weaning of neonates on mechanical ventilation.
This prospective observational study was conducted on 40 neonates on MV who were divided into 3 groups; first successful weaning group (n=25), failed weaning group (n=15) and second successful weaning group (n=15).
Comparison between first successful weaning, failed weaning and second successful weaning groups regarding Electric cardiometry parameters before extubation and after extubation revealed statistically higher significant difference in TFC before and after extubation and SVV in failed weaning group and significant difference in Cardiac index (CI) and ICON. TFC before extubation was significantly higher in failed weaning group than in successful weaning group and On comparing thoracic fluid content (TFC) between first successful weaning and second successful weaning groups before and after extubation it shows no significant difference, indicating that TFC in failed extubation patients is a reverse for lung congestion hindering extubation and after improvement of lung congestion patients were successfully extubated as indicated by the measured thoracic fluid content.
As regards TFC before extubation to detect failure cases; at cut-off point of >44, AUC was 0.997 it had 100% sensitivity and 96.0% specificity, with PPV of 93.7 and NPV of 100.0. At cut-off point of >41, AUC was 100 it had 100% sensitivity and 100% specificity, with PPV of 100 and NPV of 100.0.
Univariate analysis in this study showed that Hco3 before <= 21 was a significant predictor of weaning failure. While, multivariate logistic regression analysis revealed that Hco3 before <= 21 was insignificant predictor.
On comparing between first successful weaning, failed weaning and second successful weaning groups regarding echocardiographic parameters before and after extubation, no statistically significant difference was noted.
Comparison of echocardoigraphic parameters before extubation and after extubation among failed weaning cases showed a statistically non-significant difference. Among patients with second successful weaning LVED was significantly higher before extubation compared to after extubation. TVI was significantly lower before extubation compared to after extubation in neonates in second successful weaning group. Otherwise no significant difference was reported between neonates in second successful weaning group before and after extubation as regards ECHO parameters.
Among first successful weaning group it was revealed that LVED before extubation was significantly negatively correlated with Cardiac index (CI). SW/PW ratio before extubation was significantly correlated with SVV%. Left ventricular FS% before extubation, Ejection fraction % before extubation and heart rate showed significant correlation with ICON. Myocardial performance index (MPI) showed significant negative correlation with Cardiac index (CI).
The total duration of mechanical ventilation was significantly higher in failed group compared to first success. By univariate logistic regression analysis for factors associated with failure, Total duration of MV >6 was a significant predictor. Fio2% initial >60 was insignificant predictor while Fio2 (%) initial >65 was significant predictor.
The thoracic fluid content (TFC) by Electric cardiometer prior to extubation is good predictive of successful weaning, with high sensitivity and specificity. Thoracic fluid content assessed by electric cardiometry was insignificantly correlated with left ventricular functions assessed by ejection fraction (EF), left ventricular fractional shortening (FS) and myocardial performance index (MPI). TFC was only correlated with FS% in the failed weaning neonates.