Clinical Research Directory

Inclusion Criteria: * Adult patient admitted to the ICU within the past 72 hours * Receiving invasive mechanical ventilation * For whom the treating clinician plans to perform at least two blood bicarbonate measurements within the next 6 hours * No objection from the participant or their next of kin Exclusion Criteria: * Planned weaning from invasive mechanical ventilation or ventilator change before the second bicarbonate measurement * Conditions interfering with the interpretation of indirect calorimetry data: * Inspiratory oxygen fraction \> 60% * Administration of inhaled medications, including nitric oxide * Positive end-expiratory pressure (PEEP) \> 15 cmH₂O * Excessive leaks in the ventilator circuit, defined as expired volume \< 95% of inspired volume * Patient on mechanical circulatory support with a gas exchanger, or planned initiation before the second blood gas analysis * Patient on extracorporeal renal replacement therapy, or planned initiation before the second bicarbonate measurement * Patient who received sodium bicarbonate within 2 hours prior to inclusion, or planned administration before the second bicarbonate measurement * Frequent disconnections of the ventilator circuit, or planned bronchoscopy before the second bicarbonate measurement