الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
In spite of wide use of mechanical ventilation in the intensive care unit (ICU) in saving hundreds of lives every day, prolonged duration of ventilation can lead to increased mortality and morbidity [153], however, premature withdrawal of ventilation can result in extubation failure, which is also associated with increased morbidity and mortality.[154]
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. [155, 156]
Unfortunately, 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.[140]
SBT causes cardiac stress by increasing intrathoracic preload volume. [43, 157] Also change in lung compliance and neuromuscular weakness during SBT may cause an increase in lung de-recruitment, EVLW and impaired lung aeration leading to respiratory distress and failure. [6]
Variable methods can be used for identification of degree of lung aeration loss; one of them is CT scan of the chest that provides accurate information concerning lung aeration, however, several practical limitations are met due to difficulty to transfer ventilated patients and inability to give a dynamic image. [20]
More recently, lung ultrasound has been introduced, for assessment of lung aeration patterns. Data suggest that LUS is a good non-invasive indicator of weaning outcome. [158]
The primary aim of the current study was to determine whether clinical and ventilatory indices, or ultrasound or both, can be considered better predictors of weaning failure.
The hypothesis of the current study is to consider the lung ultrasound as a good tool in detecting the degree of lung aeration changes during ventilation, using a valid LUS score for lung aeration. This score gives a global picture of lung aeration; increasing score means that the lung aeration is lower. [67, 89]
The current study is a prospective observational study conducted in Beni-Suef university hospital in the period from October 2017 to May 2018 on 30 critically ill patients ventilated more than 48 hours.
RSBI was measured just before initiation of a SBT. Lung ultrasonography was performed to patients during positive pressure ventilation (LUS1), at the end of SBT (LUS2) and then after SBT (LUS3).
Patients were divided according to result of weaning into 2 groups; (Successful weaning group) represented by patients who were successfully weaned without the need of reintubation or non-invasive ventilation within 48 hours after weaning and the (Failed weaning group) due to failure SBT or failure of extubation within 48 hours.
The current study showed a significant comparative statistical analysis between bronchial asthma as a cause of respiratory failure and success of weaning with (P-value = 0.038)
Also there was a significant comparative statistical analysis between mean PaO2/FiO2 ratio of failed (213±70) and weaned (306.2±128.3) patients with (P-value = 0.015)
The current study showed that there was a statistically significant difference between mean LUS1, 2 and 3 (10.2±4.4) ( 6.3±2.7) ( 5.7±2.1) respectively for patients who were successfully weaned and LUS1,2 and 3 mean values for patients who failed weaning (14.3±5.3) (10.7±4.8) (13.5±5.5) respectively with (P-value<0.05).
The current study showed no statistically significant comparative statistical analysis between RSBI and weaning results.
ROC curve was applied to illustrate the potential of RSBI and LUS 1, 2 and 3 as predictors of weaning as follows:
At a cut-off value of 34.5 (25-94) the sensitivity of (RSBI) for weaning success prediction was 80 % and the specificity for prediction of failure was 30 % (AUC=0.590). PPV=69.6% and NPV=42.8%
At a cut-off value of 11.5 (1.5-20) the sensitivity of (LUS1) for prediction of weaning success was 90% and the specificity for prediction of weaning failure was 50 % (AUC=0.773).PPV=78.3% and NPV=71.4%
At a cut-off value of 8.5 (0.5-18.5) the sensitivity of (LUS2) for weaning success was 80% and the specificity for weaning failure was 70 % (AUC=0.830).PPV=84.2% and NPV=63.6%
At a cut-off value of 8.5 (2-21) the sensitivity of (LUS3) for weaning success was 85 % and the specificity for weaning failure was 100 % (AUC=0.903). PPV=100% and NPV=76.9%
Duration of mechanical ventilation was higher in failed patients (12.7±6) than that of successful group (3.7±2.4) with (P-value<0.001).
Also; length of ICU stay was higher in failed group than for successful group with mean values (19.7±7.1) (8.9±5.2) respectively and (P-value<0.001).
There was a significant linear correlation between LUS2 and length of ICU stay with (P-value =0.048). Also there was a significant comparative statistical analysis between LUS3 and mortality with (P-value =0.003).