Abstract： Objective To study the changes of trans-diaphragmatic pressure (Ptra) and its correlation with esophageal pressure (Peso) through ARDS piglet model.Methods Five piglets were enrolled in the study.Peso,gastric pressure (Pgas) and intra-thoracic pressure (Pint) was monitored through balloon inserted.The data before ARDS serve as control.ARDS was produced in the piglets through saline lavage.The pressure were observed and the Ptra were calculated.The pressure changes and correlation between Ptra and Peso were analyzed as well.Linear regression with the coefficient of determination and t-test were used as appropriate.Significance was assumed for P ＜ 0.05.Results Peso,Pgas and Pint before ARDS were 7.3 ± 1.9,25.5 ± 2.4,- 1.23 ± 0.21 cmH2O,Ptra was 18.2 ± 1.6 cmH2O.While after ARDS,the data were 4.7 ± 1.4,31.1 ± 3.1 and - 1.79 ± 0.28 cmH2O,and Ptra was 26.4 ± 2.1 cmH2 O,and all these changes were obviously ( P ＜ 0.05 ).The correlation between Pint and Peso,Pint and Ptra (A) and Ptra ( B ) were 0.93 ± 0.025,0.88 ± 0.023 and 0.87 ± 0.37 before ARDS.After ARDS,the correlation changed to be 0.82 ±0.21,0.81 ±0.20 and 0.78 ±0.31.Although a bit decreased,the correlation was still positive (P ＜ 0.01 ).Conclusions There existed good correlations between Peso and Ptra as well as between Pint and Peso before or after ARDS.Ptra was increased obviously after ARDS,which could lead to respiratory muscle fatigue.