EIT-Guided Ventilator Settings in AHRF

This exploratory study aims to investigate the effect of Electrical Impedance Tomography (EIT)-guided ventilator settings on mechanical power in patients with acute hypoxemic respiratory failure (AHRF), including both ARDS and non-ARDS conditions. Mechanical power, a key factor associated with ventilator-induced lung injury (VILI), will be measured before and after EIT-guided PEEP titration. The study will evaluate feasibility and changes in lung mechanics, gas exchange, and EIT parameters. A total of 17 patients requiring invasive mechanical ventilation will be enrolled at Siriraj Hospital, Mahidol University.

This exploratory study investigates the effect of Electrical Impedance Tomography (EIT)-guided PEEP titration on mechanical power in patients with acute hypoxemic respiratory failure (AHRF), including both ARDS and non-ARDS conditions such as severe pneumonia and pulmonary edema. Mechanical power represents the energy transferred from the ventilator to the respiratory system per unit time and has been associated with the development of ventilator-induced lung injury (VILI).

Patients who meet the inclusion criteria will undergo a standardized EIT-guided PEEP titration protocol using the Enlight 2100 EIT device. Optimal PEEP is defined as the PEEP level that minimizes both alveolar overdistension and collapse based on real-time EIT measurements. Mechanical power and other ventilatory parameters (lung compliance, plateau pressure, driving pressure, 4∆P x RR index, and gas exchange) will be assessed before and after PEEP titration at predefined time points (baseline, 2, 12, and 24 hours).

The study also evaluates the regional ventilation distribution ratios, as well as safety outcomes including hemodynamic instability, arrhythmias, and pneumothorax. Patients will be followed for up to 28 days to record duration of mechanical ventilation, ICU stay, and 28-day mortality.

This study aims to assess the feasibility and physiological benefits of personalized ventilator settings using EIT in critically ill patients with AHRF and to generate preliminary data for future interventional studies.

Eligibility Criteria:
Inclusion Criteria:

* Age ≥ 18 years
* Diagnosed with acute hypoxemic respiratory failure within 48 hours
* Expected to require invasive mechanical ventilation ≥ 48 hours
* On mechanical ventilation within 24 hours
* Deep sedation and neuromuscular blockade

Exclusion Criteria:

* Pregnancy
* Body mass index (BMI) \> 40 kg/m2
* Contraindications to using electrical impedance tomography, including
* Presence of a pacemaker or automatic implantable cardioverter-defibrillator (AICD)
* Inability to place the belt due to presence of surgical wounds dressing, thoracic or spinal cord trauma, recent thoracic surgery, etc.
* High risk for PEEP titration
* Hemodynamic instability defined as mean arterial pressure \< 65 mmHg despite optimization of fluid status and/or use of vasopressors
* Unstable cardiac arrhythmias
* Presence of lung bullae greater than 2 cm in diameter, identified on chest X-ray
* Presence of pneumothorax or pneumomediastinum
* Right-sided heart failure or severe pulmonary hypertension
* Neurologic conditions associated with a risk of intracranial hypertension
* Use of extracorporeal membrane oxygenation (ECMO)
* Severe chronic respiratory disease, defined as follows: requiring home oxygen therapy, or previous lung function showing (FEV1 less than 20 ml/kg PBW, or FEV1/FVC less than 50% predicted value), or chronic hypercapnia (PaCO2 greater than 45 mmHg) and/or chronic hypoxemia (PaO2 less than 55 mmHg) on FIO2 = 0.21, or radiographic x-ray evidence of any chronic over-inflation or chronic interstitial infiltration, or chronic restrictive, obstructive, neuromuscular, chest wall or pulmonary vascular disease resulting in severe exercise restriction (unable to climb stairs or perform household duties, secondary polycythemia, severe pulmonary hypertension with mean pulmonary arterial pressure greater than 40 mmHg)
* Decision to withhold life-sustaining treatment or palliative care.
* Moribund status with an expected survival of less than 24 hours.
* Refusal to provide informed consent