The Feasibility of Pulmonary Perfusion Assessment Using Sodium Bicarbonate Contrast With Electrical Impedance Tomography: A Prospective Pilot Study

Inclusion Criteria: * Age ≥ 18 years * Admitted to the intensive care unit (ICU) * Receiving invasive mechanical ventilation with controlled or assisted-controlled mode * Presence of a central venous catheter suitable for contrast bolus injection * Hemodynamically stable (no ongoing cardiopulmonary resuscitation; no uncontrolled shock judged by treating physician) * Expected to remain on mechanical ventilation for the duration of the EIT examination * Written informed consent obtained from the patient or legally authorized representative Exclusion Criteria: * Known pregnancy * Known allergy, intolerance, or contraindication to sodium bicarbonate or hypertonic saline * Severe arrhythmia or unstable cardiovascular status in which small bolus injection is deemed unsafe by the treating physician * Uncontrolled agitation or conditions that preclude correct EIT belt placement (e.g., extensive chest wounds, large chest dressings, chest wall deformity that prevents belt use) * Implanted electronic devices or metallic implants in the thoracic area considered a contraindication to EIT by the manufacturer's instructions * End-stage disease with expected survival of only a few hours, in whom participation is not appropriate as judged by the treating physician * Participation in another interventional trial that, in the opinion of the investigator, could interfere with EIT measurements or safety assessment