Regional Lung Inflammation and Expansion in Mechanically Ventilated Patients - a PET/CT Study

Inclusion Criteria:

- Mechanically ventilated patients scheduled to undergo a CT scanning for their routine
clinical care

- More than 24 hours of mechanical ventilation

- Less than 15 days of mechanical ventilation if patient presents ALI/ARDS (in order to
exclude the late, fibrotic, stage of ARDS).

Exclusion Criteria:

- Age less than 18 years

- Hemodynamic instability, defined as: systolic blood pressure (SBP) < 90mmHg without
the use of vasopressors or inotropic agents. We will exclude from the study patients
on vasopressors, with the exception of: dopamine up to a dose of 3 mcg/kg/min, or
norepinephrine up to 4 mcg/min, or neosynephrine up to 40 mcg/min

- Hypoxemia, defined as: PaO2 < 70 mmHg on an inspired oxygen fraction (FiO2) greater
than or equal to 0.9; FiO2 greater than or equal to 0.8 at baseline

- Patients requiring more than one vasopressor

- Hemodynamic and/or respiratory instability (as defined, respectively, in 2 and 3),
that develop when the patient is mobilized during routine nursing care

- Any acute or chronic condition which, in the opinion of the investigator, might
confound the imaging measurements (such as, but not limited to, severe bronchospasm,
pulmonary infection, and lung tumor)

- "Air leaks" requiring tube thoracostomy (e.g., pneumothorax, bronchopleural fistula)

- Pregnancy (since this is a study which would expose a fetus to radiation risk)

- Patients who have neither an arterial nor a central venous line at the time of the
enrollement