"Da Qi （大气） "is first used in Yellow Emperor’s Inner Canon （黄帝内经）

which firstly explains Da Qi’s source

position

physiology and pathology. ZHANG Zhongjing continued to use and inherit this phrase "Da Qi"from Yellow Emperor’s Inner Canon

which promoted later doctors to research Da Qi further. YU Jiayan firstly used"Da Qi in the chest"

which provided premise and basis for ZHANG Xichun to systematically research the theory of Da Qi in the chest. ZHANG Xichun firstly put forward the theory of "collapsed Da Qi in the chest"and systematically explained Da Qi in the chest and collapsed Da Qi in the chest

which marked the theory of Da Qi in the chest and the collapse became complete and mature. The theory of "Da Qi in the chest"and "collapsed Da Qi in the chest"was firstly named in Yellow Emperor’ s Inner Canon

developed by ZHANG Zhongjing and YU Jiayan

and refined and matured by ZHANG Xichun.