Through the literature screening of MyomiRX 7, the detection of mechanical ventilation group, difficult withdrawal unit and healthy adult plasma levels of MyomiRX in the evaluation of function and skeletal muscle thickness of the diaphragm, the correlation analysis of 7 kinds of MyomiRX and diaphragmatic dysfunction. The research value of this project is to explore the predictive value of plasma MyomiRX level on diaphragmatic dysfunction in patients with mechanical ventilation, and to lay the foundation for finding the target of VIDD diagnosis and treatment