1. The lung ultrasound score (LUS) will be calculated according to the observed worst ultrasound pattern and Finally, the LUSs of all the parts will added to obtain the total LUS for each patient (maximum36 points)
2. The diaphragmatic ultrasound will performed for assessment of diaphragmatic thickness and motion.

The lung ultrasound score (LUS) will be calculated according to the observed worst ultrasound pattern using the convex probe (MEDESION SONOACE R3 portable ultrasound, Korea 2010). (normal aeration, LUS = 0);( moderate loss of lung aeration (multiple, well-defined B lines), LUS = 1);( severe loss of lung aeration (multiple coalescent B lines), LUS = 2); (lung consolidation, LUS = 3).Finally, the LUSs of all the parts will added to obtain the total LUS for each patient (maximum36 points).

The diaphragmatic ultrasound will performed for assessment of diaphragmatic thickness by M-Mode Using the high frequency linear probe of 7.5 MHz.This will done in serial manner beginning 24 hours after RICU admission,then during spontaneous breathing trial till the patient is liberated from mechanical ventilation. DT difference (DTD) will be calculated by subtracting The Diaphragm thickening fraction (DTF) will calculated as: DTD/(DT at end-expiration) × 100%

The diaphragmatic ultrasound will performed for assessment of diaphragmatic motion by M-mode using the curvilinear low frequency probe (5 MHz).This will done in serial manner beginning 24 hours after RICU admission,then during spontaneous breathing trial till the patient is liberated from mechanical ventilation. Diaphragmatic excursion (DE) will identified and measured. DE amplitude will measured on the vertical axis by tracing from the baseline to the point of maximum height of inspiration on the graph.

Compare between sonographic lung aeration assessment, diaphragmatic indices and RSBI as predictors for results of weaning from MV and showing the predictive value for which parameter to predict weaning sucess alone or combining all three parameters together.