2. research objectives Objective to investigate the predictive value of specific minute RNA in plasma muscle tissue on diaphragmatic dysfunction in mechanical ventilation patients Experimental grouping (1) the control group of mechanical ventilation (time of examination, preoperative, admission to ICU and before extubation); (2) difficulty in withdrawal of units (first days, third days and seventh days after the failure of the test time for the first withdrawal); (3) the healthy control group (after the test time was selected)