The investigators conducted a prospective physiological observation study on ARDS population, described their physiological and EIT indexes with various PEEP titration methods, and also compared and analyzed those indexes to determine whether there were differences among various PEEP titration methods.The objective of this study was to explore and uncover the physiological differences in response to optimal PEEP in different ways，and analyzed the correlation of the optimal PEEP in these different ways.
Study Type
OBSERVATIONAL
Enrollment
31
Esophageal pressure was monitored with an esophageal pressure catheter
West China Hospital of Sichuan University, Chengdu
Chengdu, Sichuan, China
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
Time frame: through study completion, an average of 1 year
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.
Time frame: baseline, within 5 minutes after the PV-tool measurement, and within 5 minutes after each increment and decrement of PEEP during the PEEP adjustment process
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.
Time frame: baseline, within 5 minutes after the PV-tool measurement, and within 5 minutes after each increment and decrement of PEEP during the PEEP adjustment process
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
Time frame: baseline, within 5 minutes after the PV-tool measurement, and within 5 minutes after each increment and decrement of PEEP during the PEEP adjustment process
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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).
Time frame: baseline, within 5 minutes after the PV-tool measurement, and within 5 minutes after each increment and decrement of PEEP during the PEEP adjustment process
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).
Time frame: baseline, within 5 minutes after the PV-tool measurement, and within 5 minutes after each increment and decrement of PEEP during the PEEP adjustment process
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
Time frame: baseline, within 5 minutes after the PV-tool measurement, and within 5 minutes after each increment and decrement of PEEP during the PEEP adjustment process
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).
Time frame: baseline, within 5 minutes after the PV-tool measurement, and within 5 minutes after each increment and decrement of PEEP during the PEEP adjustment process
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
Time frame: baseline, within 5 minutes after the PV-tool measurement, and within 5 minutes after each increment and decrement of PEEP during the PEEP adjustment process
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 %
Time frame: baseline, within 5 minutes after the PV-tool measurement, and within 5 minutes after each increment and decrement of PEEP during the PEEP adjustment process
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: %).
Time frame: baseline, within 5 minutes after the PV-tool measurement, and within 5 minutes after each increment and decrement of PEEP during the PEEP adjustment process
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: %).
Time frame: baseline, within 5 minutes after the PV-tool measurement, and within 5 minutes after each increment and decrement of PEEP during the PEEP adjustment process