Temporal Dynamics of CO2 Equilibration Following Ventilator Adjustment: Comparison of Flow-Based (V?CO2) and Partial Pressure-Based (PaCO2 and etCO2) Markers

INTERVENTION: Group 1: Intervention Group 1 – Lung‐Protective Tidal Volume (VT 6 mL/kg PBW) Participants assigned to this group will be mechanically ventilated with a tidal volume of 6 mL/kg predicted body weight (PBW). Initially, a minute ventilation of 96 mL/kg PBW will be achieved using a respiratory rate of 16 breaths per minute. Subsequently, minute ventilation will be increased to 144 mL/kg PBW by increasing the respiratory rate to 24 breaths per minute, while maintaining a constant tidal volume. Following the ventilatory intervention, arterial blood gas analyses will be performed repeatedly over a 20‐minute observation period, while respiratory monitoring parameters will be recorded continuously to characterize the temporal dynamics of carbon dioxide equilibration. Group 2: Intervention Group 2 – Conventional Tidal Volume (VT 8 mL/kg PBW) Participants assigned to this group will be mechanically ventilated with a tidal volume of 8 mL/kg predicted body weight (PBW). An initial minute ventilation of 96 mL/kg PBW will be achieved using a respiratory rate of 12 breaths per minute. Subsequently, minute ventilation will be increased to 144 mL/kg PBW by increasing the respiratory rate to 18 breaths per minute, while maintaining a constant tidal volume. Following the ventilatory intervention, arterial blood gas analyses will be performed repeatedly over a 20‐minute observation period, while respiratory monitoring parameters will be recorded continuously to characterize the temporal dynamics of carbon dioxide equilibration. CONDITION: Change of respirator settings PRIMARY OUTCOME: The primary endpoint is the dynamics of arterial carbon dioxide partial pressure (PaCO2) equilibration following a standardized ventilatory intervention, operationalized as the time to 50% equilibration of PaCO2 (t50(PaCO2)), defined as the time required to reach 50% of the total change in PaCO2 after the ventilatory intervention. SECONDARY OUTCOME: ‐ Time to 50% equilibration of end‐tidal carbon dioxide (t50etCO2) ; ‐ Time to 50% equilibration of carbon dioxide elimination (t50V?CO2) ; ‐ Comparison of equilibration times (t50) between PaCO2, etCO2, and V?CO2 ; ‐ Characterization and comparison of the temporal response patterns of PaCO2, etCO2, and V?CO2 during the first 20 minutes following the ventilatory intervention INCLUSION CRITERIA: ‐ Elective surgery under total intravenous general anesthesia (TIVA) ‐Routine placement of an arterial catheter for perioperative blood gas analysis according to institutional standard operating procedures ‐ Written informed consent prior to study participatio