Effects of Sedation on Transpulmonary Pressure and Lung Homogenous (ARDS)

Inclusion Criteria:

1. ARDS group patient (1) Acute onset of all of the following criteria within a 48-hour period:

   1. Requires positive pressure ventilation through an endotracheal tube
   2. Bilateral infiltrates consistent with edema on frontal chest radiograph, with a duration of no more than 7 days
   3. PaO2/FiO2 less than 300 while receiving positive end-expiratory pressure (PEEP) at more than 5 cm H2O for at least 4 hours, with a duration of no more than 7 days
   4. No clinical evidence of left atrial hypertension (2) Hemodynamics stable (dopamine <10ug/kg•min or norepinephrine <10ug/kg)
2. Surgical patient Surgical patient requires positive pressure ventilation through an endotracheal tube PaO2/FiO2 more than 300 Hemodynamics stable (dopamine <10ug/kg•min or norepinephrine <10ug/kg)

Exclusion Criteria:

• Age younger than 18 years or older than 85 years
• Cardiac failure
• Known pregnancy
• Increased intracranial pressure
• Severe neuromuscular disease
• Recent injury or other pathologic condition of the esophagus
• Pneumothorax
• Pleural effusion
• Diaphragmatic hernia
• Severe chronic respiratory disease
• End-stage chronic organ failure
• Expected survival of less than 24 hours
• Participation in another interventional study
• Attending physician declines to give consent for participant to enroll
• Patient or surrogate declines or is unable to give consent