Post-hoc Analysis of Regional Pulmonary Perfusion and Hemodynamic Parameters Measured by Electrical Impedance Tomography

Inclusion Criteria: * Age 18 - 80 years * Mandatorily ventilated intensive-care patients with impairment in oxygenation (P/F ratio \< 300 at PEEP ≥ 5) ventilated at a positive end-expiratory pressure (PEEP) not exceeding 10 mbar and an fraction of inspired oxygen (FiO2) chosen, such that pulse oximetry is sensitive towards arterial oxygen pressure (PaO2) changes. * Expected ventilation time \>48h * Existing central venous and arterial access * Chest circumference 70 - 150 cm * Mandatory mechanical ventilation (patients without spontaneous efforts) * Serum levels of sodium and chloride within normal range * Cardiac output monitoring in place (PICCO) Exclusion Criteria: * Contraindication to central venous injection of 5 % sodium chloride (NaCl) (e.g. elevated Na+ and/or Cl- concentration: Na+ should not exceed 150 mmol/l, Chloride should not exceed 115 mmol/l, known hypernatremia, known high serum osmolality) * Contraindications of PulmoVista 500: * Patients with pacemakers, defibrillators or other electrically active implants * Patients with damaged skin or impaired skin contact of the electrodes due to wound dressings * Patients where the attachment of the patient belt could pose a risk to the patient, e.g. patients with spinal lesions or fractures * Patients with uncontrolled body movements * Extremely obese patients (BMI\>50) * Patients during pregnancy * Patients with massive lung edema * Use during electricity-based therapies, such as electrosurgery or electrocautery * Use in the presence of strong magnetic fields * Use in conjunction with other bioimpedance measurement devices * Infection or colonization with multi-resistant pathogens that require isolation of the patient (e.g. MRSA)