Mnemonic : ARDS A: Airway and Aspiration : 1- gastric aspiration . 2- Airway injury ( smoke inhalation , drowning ) . R: Related lung infection : 1- Pneumonia. 2- Tuberculosis . D: Direct lung injury : 1- Chest trauma . 2- Fat embolism . 3- Toxins inhalation ( ammonia ) . S : Systemic causes : 1- Pancreatitis . 2- Sepsis . 3- Massive blood transfusion.