Intra-abdominal hypertension can increase the pleural pressure, and then end-expiratory transpulmonary pressures will be turn to negative, Pulmonary atelectasis/acute lung injury/acute respiratory distress syndrome will appear. In the group of people who suffering intra-abdominal hypertension, the investigators use the pressure of esophagus to speculate the Intrathoracic pressure, and to setting PEEP in order to decrease the happening of ALI/ARDS, which may decrease morbidity in this population.

Inclusion Criteria:

• intra-abdominal hypertension
• mechanical ventilation
• sedation

Exclusion Criteria:

• underlying pulmonary disease
• age older than 60 years and younger than 18 years
• vital signs were not stable
• non voluntary