Bedside PEEP Selection in by Electrical Impedence Tomography During Mechanical Ventilation in Children

The study enrolled consecutive patients under 3 years of age who required mechanical ventilation due to impaired oxygenation or altered respiratory mechanics. Impaired oxygenation sufficient for inclusion was defined as an oxygenation index (OI) greater than 4, defined as mean airway pressure multiplied by FiO₂ divided by PaO₂, and/or an oxygen saturation index (OSI), defined as mean airway pressure multiplied by FiO₂ divided by SpO₂, greater than 5. Altered respiratory mechanics sufficient for inclusion was defined as reduced respiratory system compliance normalized to body weight (Crs/kg) below 0.7 mL/cmH₂O/kg.

Patients were excluded if they had contraindications to the placement of the EIT belt, such as thoracic fractures, chest drains, or subcutaneous thoracic devices. The presence of intracardiac shunts was also an exclusion criterion. Further exclusions included confirmed or suspected pneumothorax on chest X-ray or lung ultrasound, hemodynamic instability requiring adrenaline or noradrenaline at doses exceeding 0.05 mcg/kg/min, or a reduction in systolic blood pressure greater than 30% during recruitment maneuvers. Technical issues that prevented reliable acquisition of EIT signals, including prolonged signal instability, belt-to-chest size incompatibility (< 3 kg), or the need for urgent clinical interventions, also led to exclusion. Lack of informed consent from parents or legal guardians precluded enrollment.

Study Protocol The stepwise PEEP titration protocol used in this study is partially part of a clinical approach routinely adopted in the PICU of our institution to optimize lung recruitment and individualize ventilator settings in mechanically ventilated children.

According this study protocol, once clinical stabilization was achieved - defined as adequate sedation and analgesia, cardiovascular stability, and appropriate patient-ventilator synchrony -neuromuscular blockade was administered. An EIT belt with 16 electrodes (PulmoVista® 500, Dräger Medical GmbH, Lübeck, Germany) appropriate to the patient's weight was placed at the fourth or fifth intercostal space along the axillary line.

Baseline parameters were collected, including gas exchange data, respiratory mechanics, and ventilator settings (PEEP, tidal volume [Vt], respiratory rate, driving pressure [ΔP], compliance [Crs], FiO₂, SpO₂, OI or OSI), as well as blood gas analysis when available. PEEP was initially set according to the ARDSNet lower PEEP/higher FiO₂ table, referred to as PEEPnih. If children was volume-controlled ventilate, pressure-controlled ventilation was applied with an inspiratory pressure above PEEP equal to the baseline ΔP to maintain a similar Vt regardless of the previous ventilation mode.