ARDS受试者的各种策略的增量和减少窥视滴定：一项前瞻性生理研究 (ARDS，PEEP)

the selected PEEP values

1. 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 at each selected PEEP

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.

respiratory system compliance value at each selected PEEP

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

plateau pressure 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

Driving Pressure at each selected PEEP

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).

End-inspiratory Transpulmonary Pressure (PTPi) at each selected PEEP

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).

End-expiratory Transpulmonary Pressure (PTPe) at each selected PEEP

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

transpulmonary driving pressure at each selected PEEP

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).

EIT-derived Regional Ventilation Parameters at each selected PEEP level

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) at each selected PEEP level

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 %

CL HP% (overdistension region) at each selected PEEP level

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: %).

CL LP% (collapse region) at selected PEEP

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: %).