الفهرس 
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Abstract
Summary
Mechanical ventilation is a widely used intervention that could help in saving hundreds of lives of critically ill patients every day. However, prolonged duration of ventilation can lead to increased mortality and morbidity; also, premature withdrawal of ventilation can result in extubation failure, whichisalsoassociatedwithin-creasedmorbidityandmortality[223]Therefore,there is no doubt that identification of the ideal time for withdrawal of mechanical ventilation is of utmost importance in improving morbidity, mortality and ICU outcomes. [224]
Regrettably, the pathophysiology of weaning failure is complex and is not completely understood. Known risk factors of weaning failure have considerable crossover, especially those related to the heart and lungs.[172]Among causes of weaning failure, weaning induced pulmonary edema which is related to transition of the patient from positive pressure regimen of ventilation to a negative pressure mode; thus, leading to subsequent hemodynamic changes. This process is related to the occurrence of diastolic dysfunction and inability of the LV to accommodate increasing venous return with subsequent accumulation of fluids in interstitial spaces in lungs. [225]
Variable methods can be used for identification of the cardiac dysfunc-tion and weaning induced pulmonary edema; depending on assessment of the cardiac filling pressures, cardiac strain and interstitial pulmonary con-gestion.[226]Recently, lung ultrasoundhas been introduced, for assessment oflung aeration patterns. Data suggest that LUS can be used as a good non-invasive indicator of weaning outcome. [227]Moreover, echocardiography can be used in assessment of LV diastolic dysfunction by the use of TDI to predict the inability of the heart to accept the increasing volume load during the weaning process. [15]Multiple studies have also revealed that the weaning process represents , to some extent, a degree of cardiac strain which can be assessed through the serum measurement of cardiac peptides in-cluding BNP and NT-proBNP, thus predicting the extent of cardiac dysfunction and its impact on the weaning process.[82]
The primary aim of the current study was to assess the validity and reliability of lung ultrasonography, echocardiography and serum NT-proBNP in assessment of the heart and lung dynamics during mechanical ventilation and to study its impact on the outcome of mechanically ventilated patients.
The current study is a prospective observational study, conducted in the Critical Care Department of Beni-Suef University, from December 2018 to August 2019, on 40 critically ill patients who were invasively ventilated for more than 48 hours.
Patients ready for weaning were subjected to the study measurements before and 30 minutes after initiation of the SBT. Patients were then fol-lowed during weaning and 48 hours after successful weaning to detect failed weaning or re-intubation. Patients were then classified into successful and failed weaning groups. Patients were then followed for 28 days to follow the secondary outcomes.
During PPV, clinical, laboratory, ABG and ventilator data were col-lected. Also, echocardiography, lung ultrasonography and serum NT-proBNP were measured. After that, included patients were subjected to a SBT, for 2 hours, using (PSV) with pressure support (5-10 cmH2O). ABG, ventilator data, echocardiography, lung ultrasonography, and NT-proBNP were measured; 30 minutes after the start of SBT.
Most of included patients were admitted with sepsis with a pulmonary source in most of scenarios. This carried a higher rate of failed weaning (57.5%) and a higher rate of mortality (65%).
Lung ultrasonography was used to assess lung aeration, before and 30 minutes after the start of SBT, through calculation of the Lung Ultrasound Score (LUS). Each hemithorax was divided into 4 regions (2 anterior and 2 lateral) to detect one out of four aeration patterns and to calculate a score ranging from (0-24). Both of LUS1 and LUS2 measurements were signifi-cantly higher in the failed weaning group of patients (P = 0.006 and 0.026) respectively.
NT-proBNP was used as a marker of cardiac strain and dysfunction by the use of immunofluorescence chromatography assay method before and during the SBT. However, no significant relation was found between these measurements and weaning results.
Echocardiography was also done during PPV and during SBT. LV di-astolic dysfunction and RV systolic dysfunctions were significantly related to the study outcome. E /e\ was higher in the failed weaning group (P = 0.005 and 0.002) for both readings. Moreover, TAPSE was lower in the failed weaning group (P = 0.004). Additionally, PASP was higher in non-survivors rather than survivors (P = 0.041 and 0.037)for both measure-ments.
ROC curve was blotted to detect the best cu-off point for diagnosis of impaired heart and lung dynamics during mechanical ventilation. E/e\ (2) could predict weaning failure at a cut-off; 8 with the best sensitivity of all measurements (82.6%). Moreover, NT-proBNP (1) at a cut-off; 512.5 pg/mland NT-proBNP (2) at a cut-off; 575pg/ml could predict the failure of weaning with the best specificity of all other measures (70.6 % for both measurements). Additionally, both of LUS1 and LUS2 could be used as predictors of weaning failure at cut off value of 5.5 with a sensitivity of 73.9%.