Incremental and Decremental PEEP Titration by Diverse Strategies in Subjects With ARDS: A Prospective Physiological Study

• Method-specific selected PEEP values

• Description: The principal endpoint was the set of 15 method-specific selected PEEP values determined for each patient.
• Unit of Measure: cmH₂O

SpO2/FiO2 measured at each selected PEEP. This study will separately measure peripheral oxygen saturation (SpO₂, unit: %) and fraction of inspired oxygen (FiO₂, unit: %). Because both measurements share the same unit (%), they will not be reported as separate outcome measures. Instead, they will be aggregated into a single reported value: the SpO₂/FiO₂ ratio (dimensionless). At each selected positive end-expiratory pressure (PEEP) level, the ratio will be calculated as S/F = SpO₂ (%) ÷ FiO₂ (%), and this ratio will be recorded as the final outcome measure.

This study will directly record the respiratory system compliance value as measured and displayed by the ventilator (unit: mL/cmH₂O) at each selected PEEP.

At each selected positive end-expiratory pressure (PEEP) level, plateau pressure will be directly recorded from the ventilator after performing an inspiratory hold maneuver. This value is displayed by the ventilator in cmH₂O

At each selected positive end-expiratory pressure (PEEP) level, plateau pressure (Pplat, unit: cmH₂O) will be measured via the ventilator, and the corresponding PEEP value (unit: cmH₂O) will be recorded. Driving pressure (ΔP) is calculated as the difference between the two: ΔP = Pplat - PEEP (unit: cmH₂O).

After placement of an esophageal pressure catheter, the ventilator will monitor esophageal pressure (Pes) and airway pressure. At each selected positive end-expiratory pressure (PEEP) level, an end-inspiratory hold maneuver will be performed. The end-inspiratory transpulmonary pressure (PTPi) is calculated as the difference between the airway plateau pressure (Pplat) measured during the hold and the corresponding esophageal pressure (Pes): PTPi = Pplat - Pes (unit: cmH₂O).

After placement of an esophageal pressure catheter, the ventilator will monitor esophageal pressure (Pes) and airway pressure. At each selected positive end-expiratory pressure (PEEP) level, an end-expiratory hold maneuver will be performed. The end-inspiratory transpulmonary pressure (PTPe) is calculated as the difference between the PEEP measured during the hold and the corresponding esophageal pressure (Pes): PTPe = PEEP - Pes (unit: cmH₂O). This calculated value is the single reported outcome measure

After placement of an esophageal pressure catheter, the ventilator will monitor transpulmonary pressures. At each selected PEEP level, end-inspiratory transpulmonary pressure (PTPi) and end-expiratory transpulmonary pressure (PTPe) are obtained during inspiratory and expiratory hold maneuvers, respectively. Both are measured in cmH₂O. Transpulmonary driving pressure is calculated as the difference: ΔPtp = PTPi - PTPe (unit: cmH₂O).

Using electrical impedance tomography (EIT), the lung is divided into four regions of interest (ROI I to ROI IV) from ventral to dorsal. For each ROI, the percentage of tidal impedance variation relative to total tidal impedance variation is recorded (% of total). unit: cmH₂O

the center of ventilation (COV) is calculated as the position of the ventilation center along the ventral-dorsal axis, expressed as a percentage (0% = ventral, 100% = dorsal). this parameter is measured in %

Using electrical impedance tomography (EIT)，based on regional compliance analysis，CL HP% represent the percentage of lung regions showing a decrease in compliance at high PEEP due to overdistension (unit: %).

Using electrical impedance tomography (EIT)，based on regional compliance analysis，CL LP% represent the percentage of lung regions showing a decrease in compliance at low PEEP due to collapse (unit: %).