Relevant studies have shown that in the rat model of ARDS caused by lipopolysaccharide, the ACE activity of bronchoalveolar lavage fluid significantly increased, the corresponding expression of Ang II increased and the expression of ACE2 and Ang(1-7) decreased.22 It is suggested that ARDS is due to RAS system imbalance, which was reflected in the increase of ACE-Ang II axis activity, and the decrease of ACE2-Ang(1-7) axis activity. Here, ACE is linked to acute respiratory distress syndrome.