Overview
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.
Description
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:
- PEEP titration targeted to achieve the best static compliance of the respiratory system.
- 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.
Eligibility
Inclusion Criteria:
- Diagnosis of moderate or severe Acute Respiratory Distress Syndrome (ARDS) according to the Berlin definition: acute onset, bilateral opacities not fully explained by heart failure or fluid overload, and Partial pressure of oxygen in arterial blood/Fraction of inspired oxygen \<= 200 mmHg with Positive End-Expiratory Pressure (PEEP) \>= 5 cmH2O.
- ARDS duration \< 36 hours since fully meeting Berlin consensus criteria.
- Relative hemodynamic stability: absence of refractory shock, defined as norepinephrine dose \<= 0.5 mcg/kg/min.
Exclusion Criteria:
- Evidence of active pulmonary air leaks (bronchopleural fistula, pneumothorax, pneumomediastinum).
- Severe uncorrected hemodynamic instability (norepinephrine \> 0.5 mcg/kg/min).
- Contraindications for esophageal balloon placement (esophageal obstruction, known perforation, recent esophageal surgery, severe esophagitis).
- Elevated intracranial pressure or conditions where hypercapnia-induced increases in intracranial pressure must be avoided (intracranial hemorrhage, cerebral contusion, cerebral edema, mass effect with midline shift on CT).
- Known pregnancy.
- Severe coagulopathy (platelet count \< 5,000/uL or INR \> 3).
- Airway opening pressure higher than 15 cmH2O (AOP \> 15 cmH2O).
- History of severe neuromuscular disease or chronic respiratory disease.
- Having received invasive mechanical ventilation for more than 96 hours.
- Inability to obtain informed consent or refusal by the legal representative.
- Contained laparotomy (open abdomen).
