الفهرس 
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Abstract
The appropriate timing of extubation is crucial in critically ill patients who are weaned from invasive mechanical ventilation. Early extubation causes post-extubation respiratory failure that result in reintubation and poor outcomes. Delayed extubation can lead to further complications like (VAP) ventilator associated pneumonia and diaphragmatic dysfunction that cause weaning failure from mechanical ventilation. Therefore, deciding the appropriate time for extubation remains a challenge to intensivists who care for critically ill patients.
The diaphragm is subjected to various adverse factors in critical patients, such as hypoxia, sepsis, electrolyte imbalance, and neuromuscular blocking agents in addition to mechanical ventilation, which causes ventilator-induced diaphragmatic dysfunction by decreasing the force-generating capacity of diaphragm, therefore the assessment of diaphragm dysfunction is important in patients subjected to weaning or extubation trial as the diaphragm is the primary muscle of inspiration used for spontaneous breathing because it contributes to 70% of the tidal volume during inspiration in normal people.
Fluoroscopic examination of the diaphragm remains the gold standard for evaluation of diaphragmatic movement, but it cannot be performed in patients in the ICU. Ultrasound is a promising tool that was recently used by researchers to detect diaphragmatic dysfunction being bedside, non -invasive, cheap, simple, radiation free tool. Diaphragm function can be assessed by two parameters, namely excursion and diaphragm thickness change during spontaneous breathing trial. In current study, these two parameters were compared with each other to determine which one can predict better successful extubation.
This prospective study was carried out on 50 patients who are mechanically ventilated at ICU units of Ain shams university hospital, All patients had successfully undergone a successful spontaneous breathing trial. Ultrasound of diaphragmatic thickness fraction and diaphragmatic excursion were assessed by ultrasound prior to extubation while breathing spontaneously on a T-piece. After extubation patients clinical status were followed up for 48 hr and were classified according outcome into.
A) Successful extubation was defined as spontaneous breathing for>48hr following extubation without appearance any signs of respiratory fatigue, change of mental status and hemodynamic unstability.
B) Failed extubation was defined reintubation or need of non invasive mask ventilation during the 48 hour following extubation.
In current study we found that diaphragmatic excursion more predictive than the diaphragmatic thickness fraction as a predictor of weaning from mechanical ventilation with diaphragmatic excursion the cut off value 1cm, the sensitivity was 82%, the specificity was 78% and accuracy was 73%.
Regarding the diaphragmatic thickness fraction cut off value was 21.5%, the sensitivity was76%, specificity was 71% and accuracy was 94%.
In current study we found that the diaphragmatic ultrasonography was found to be a promising tool for predicting the extubation outcome for mechanically ventilated patients.