Background: Acute respiratory distress syndrome (ARDS) patients require careful assessment before extubation to prevent failure, which is associated with poor outcomes. While current guidelines recommend weaning protocols, these are based on general respiratory failure studies rather than ARDS-specific data. Esophageal pressure (Pes) measurement provides direct assessment of inspiratory effort but is rarely utilized clinically.

Objectives: This Japanese sub-study of EXTEND ARDS aims to evaluate whether:

1. ΔPes measurements during spontaneous breathing trials (SBT) can predict SBT failure
2. ΔPes measurements post-extubation can predict 48-hour extubation failure

Methods: This prospective observational study will be conducted in Japanese ICUs. Esophageal pressure will be measured using standardized Nutrivent balloons (4mL volume) with Hamilton ventilators. Balloon placement in the lower third of the esophagus will be confirmed by cardiac artifacts and chest X-ray. ΔPes will be calculated as the difference between end-expiratory and peak inspiratory esophageal pressure, excluding esophageal contractions.

Significance: This study addresses a knowledge gap regarding the utility of esophageal pressure monitoring in ARDS patients during mechanical ventilation weaning. Findings may help optimize extubation timing and improve patient outcomes through objective physiological measurements.

1. Background Acute respiratory distress syndrome (ARDS) remains a life-threatening condition with high mortality among mechanically ventilated patients. While current guidelines recommend weaning protocols for extubation, these are primarily based on studies of general acute respiratory failure rather than ARDS-specific populations.

   Inspiratory effort assessment during liberation from mechanical ventilation traditionally relies on respiratory rate monitoring during spontaneous breathing trials (SBT). However, esophageal pressure (Pes) measurement, which provides direct measurement of inspiratory effort, is rarely utilized in clinical practice. This is particularly relevant in ARDS patients, where excessive inspiratory effort can induce pendelluft phenomenon, potentially causing dorsal lung injury in the supine position.

   Recent studies have shown that diaphragmatic contraction, maximum inspiratory pressure, ΔPes, and trans-diaphragmatic pressure can predict successful weaning in prolonged mechanical ventilation patients. However, there remains a significant knowledge gap regarding the utility of esophageal pressure measurements in predicting SBT and extubation success specifically in ARDS patients.

2. Study Significance This Japanese sub-study of the EXTEND ARDS trial will investigate whether ΔPes measurements during SBT and post-extubation can predict extubation outcomes in ARDS patients. By incorporating esophageal pressure monitoring, this study aims to provide objective physiological data to improve the prediction of extubation success and optimize the timing of liberation from mechanical ventilation.

3. Study Design and Methods This is a prospective observational sub-study conducted in Japanese ICUs. Esophageal pressure will be measured using Nutrivent balloons with Hamilton C6 or G5 ventilators. The balloon placement will be confirmed by cardiac artifacts and chest X-ray, positioned in the lower third of the esophagus. Balloon volume will be standardized at 4mL, following manufacturer recommendations and GLOBAL WEAN study protocols.

4. Primary Objectives

To evaluate whether:

1. ΔPes measurements during SBT can predict SBT failure
2. ΔPes measurements post-extubation can predict extubation failure within 48 hours

Inclusion Criteria:

1. Adult mechanically ventilated patients (≥ 16 years old) with esophageal pressure monitoring, expected to receive invasive mechanical ventilator for more than 48 hours
2. Patients who meet the diagnosis of ARDS at the start of invasive mechanical ventilation based on a new global definition of ARDS.

Exclusion Criteria:

1. Patients who already had tracheostomy at the start of invasive mechanical ventilation
2. Patients who were transferred to participating hospital more than 2 days after the start of invasive mechanical ventilation
3. Patients with terminal conditions at the start of invasive mechanical ventilation
4. Patients who have expressed their refusal to have their clinical data used in research

Adult mechanically ventilated patients (≥ 16 years old) expected to receive invasive mechanical ventilator for more than 48 hours

Study protocol