LUNG INFECTION in ICU (LUNG-I3)

Inclusion Criteria: All the following criteria * Age 18 years or greater * Severe ICU patients hospitalized for one of the above diseases: * Septic shock (requirement of vasopressor to maintain a mean arterial pressure of 65 mm Hg or greater and serum lactate level greater than 2 mmol/L (\>18 mg/dL) in the absence of hypovolemia) caused either by pneumonia (n=20) or another source n=20) * Severe trauma (level I and II), Injury Severity Score ≥ 25 OR * Burn with TBSA over 20% * NAD \> 0.1 µg/kg/min * At least 2 SOFA criteria ≥ 2 points Exclusion Criteria: * Aspiration pneumonia * Unable to obtain a valid and written consent from a patient or their legally authorized representative in accordance with the local regulatory instances (this includes in FR: Person not affiliated to a health insurance scheme, or not a beneficiary of such a scheme. Persons who are the subject of a legal protection order. Person with restricted freedom following a legal or administrative decision and a person admitted without their consent pursuant to Articles L.3212-1 and 3213-1, which are not included in Article L.1121-8 of the French Public Health Code.) * COPD * Smoke inhalation in burn patients * Participation in an intervention study * Pregnant or breastfeeding women * Immunocompromised patients, defined as * patients with solid tumors with chemotherapy in the last 3 months or a progressive metastatic disease * hematologic malignancies * solid organ transplantation * HIV infection with or without AIDS * treatment with corticosteroids (\> 3 months at any dosage or ≥ 1 mg/kg prednisone equivalent per day for \> 7 day) * treatment with other immunosuppressive drugs.