Purpose:Find the relationship between tidal volume and lung strain in ARDS patients.Then find the most suitable tidal volume for each patient according to the dividing value.~Methods:Measure the lung strain in the tidal volume of 6mL/kg,8mL/kg,10mL/kg and 12mL/kg in each ARDS patient.~Hypothesis:With the increase of the tidal volume,the lung strain develops.In the patient with larger lung compliance,the strain of the group of conventional tidal volume is less than 0.27 and there is no obvious difference between the group of small tidal volume.
Measure the lung strain in different tidal volume in ADRS patients to find the relationship between tidal volume and lung strain and find the most suitable tidal volume for each patient.