Influence of Lung Recruitment Potential on Positive End-Expiratory Pressure (PEEP) Titration Strategies in Acute Respiratory Distress Syndrome (ARDS) Patients.

ARDS (Acute Respiratory Distress Syndrome)

Acute Respiratory Distress Syndrome, Positive End-Expiratory Pressure, Respiratory Mechanics, Lung Volume Measurements, Esophageal Monitoring, Ventilator-Induced Lung Injury, Artificial Respiration

Acute Respiratory Distress Syndrome (ARDS) is characterized by severe hypoxemia and diffuse alveolar collapse, often requiring invasive mechanical ventilation. Non-individualized mechanical ventilation settings can cause ventilator-induced lung injury (VILI). Positive end-expiratory pressure (PEEP) prevents alveolar collapse, but its effect varies among individuals. The recruitment-to-inflation (R/I) ratio evaluates bedside lung recruitment potential. This pilot study aims to compare two individualized PEEP titration strategies-one guided by the best static respiratory compliance and another guided by transpulmonary pressure via an esophageal balloon-and evaluate how baseline lung recruitment potential alters the early physiological responses to these interventions. Both strategies are preceded by an identical, standardized pressure-controlled initial lung recruitment maneuver to establish a baseline recruitment state.

This is a prospective, randomized, open-label, parallel-group pilot study conducted at the Adult Intensive Care Unit of Hospital Dr. Franco Ravera Zunino (HFRZ). Eligible adult patients under invasive mechanical ventilation with moderate-to-severe ARDS within 36 hours of fulfilling Berlin criteria will be evaluated. Prior to randomization, the patient's recruitment potential will be measured bedside using the R/I ratio (where \> 0.5 indicates high recruitment potential and \<= 0.5 indicates low potential). Eligible participants will then be randomized 1:1 into two PEEP titration groups: 1. PEEP titration targeted to achieve the best static compliance of the respiratory system. 2. PEEP titration guided by transpulmonary pressure measured via an esophageal balloon to target a positive end-expiratory transpulmonary pressure. Crucially, immediately before starting the specific PEEP titration protocol in either group, an identical, standardized lung recruitment maneuver will be performed. This maneuver is executed in pressure-controlled ventilation (PCV) with a control pressure of 15 cmH2O, I:E ratio of 1:1, FiO2 1.0, starting with PEEP 5 cmH2O and increasing by 5 cmH2O every 10 seconds up to PEEP 25 cmH2O, maintaining a maximum peak pressure limit of 40 cmH2O for exactly 1 minute. Standard baseline ventilator parameters will follow protective ventilation targets: volume-controlled ventilation, tidal volume 6-8 mL/kg of predicted body weight, respiratory rate adjusted to keep pH 7.25-7.45, plateau pressure \< 28 cmH2O, and driving pressure \< 14 cmH2O. Physiological parameters (PaO2/FiO2, driving pressure, ventilatory ratio, static compliance) will be recorded at 1, 24, 48, and 72 hours. The primary outcome is the change in oxygenation (PaO2/FiO2 ratio) at 24 hours. The study will explore how the baseline phenotype of lung recruitability alters early mechanical and gas exchange outcomes.

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