Adaptive Support Ventilation in Acute Respiratory Distress Syndrome (ARDS)

Inclusion criteria: Study to include at least 40 patients admitted to RICU with diagnosis of ARDS as defined by American European consensus committee in 1994. 1. Acute onset shortness of breath(\<7 days) 2. PaO2/FiO2 \< 200 mm Hg (regardless of PEEP) 3. Bilateral infiltrates on frontal chest radiograph 4. \<18 mm Hg when measured or no clinical evidence of left atrial hypertension Exclusion criteria: 1. Age less than 12 years 2. Patients having underlying chronic lung disease (COPD, interstitial lung disease, pulmonary hypertension) 3. Contraindication to permissive hypercapnea (raised intracranial pressure, acute cerebrovascular disorders, acute or chronic myocardial ischemia, right ventricular failure, uncorrected severe metabolic acidosis, sickle cell anemia, tricyclic antidepressant overdose, pregnancy)