The purpose of this observational study is to assess the differences and consistency in evaluating lung recruitment potential between the recruitment-to-inflation ratio (R/I ratio) and three-dimensional electrical impedance tomography (3D-EIT) and two-dimensional EIT (2D-EIT) in mechanically ventilated patients with acute respiratory failure. The main questions it aims to answer is:
Are the lung recruitment potentials predicted by 3D-EIT, 2D-EIT and the R/I ratio consistent? Participants will: Undergo a standardized PEEP titration protocol with synchronized EIT monitoring; Have R/I ratios measured at high and low PEEP levels.
Mechanically ventilated patients under sedation and analgesia with no spontaneous breathing.
Oxygenation index < 300 mmHg.
Patients who are clinically judged by the attending doctor to require the PEEP titration.
Aged under 18 years.
Pregnancy.
Contraindications for EIT examination (e.g. automatic implantable cardioverter defibrillator, implantable pumps, chest wounds limiting electrode belt placement, severe thoracic deformity, and others).
No informed consent obtained.
Patients with acute respiratory failure who are intubated, under sedation and analgesia with controlled ventilation and no spontaneous breathing will be recruited from the Department of Critical Care Medicine, Peking Union Medical College Hospital. Additional inclusion criteria include an oxygenation index of less than 300 mmHg, clinical judgment indicating the need for PEEP titration, and no contraindications to PEEP titration or EIT examination.
Case-only
Prospective
The lung recruitment potential assessed and PEEP titration by ventilator and 2D/3D EIT
Diagnostic testThe patient will undergo a standardized PEEP titration procedure and determination of the Recruitment-to-Inflation ratio (R/I ratio), with concurrent monitoring by both 2D- and 3D- EIT.
Lung recruitment assessed by R/I ratio and 2D/3D-EIT （PEEP titration）
Lung recruitment potential can be predicted by the R/I ratio and the lung collapse rate calculated from 2D/3D-EIT.
R/I ratio measured by 2D/3D-EIT
The R/I ratio can be calculated from 2D/3D-EIT.
V/Q monitored by EIT
Ventilation and perfusion monitored by 2D/3D-EIT at different PEEP levels. To evaluate the V/Q match, deadspace and shunt lung region.
SpO₂ at different PEEP levels
Pulse oxygen saturation at different PEEP levels
Lung compliance at different PEEP levels
Lung compliance at different PEEP levels measured via ventilator parameters
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