Ultraprotective Lung Ventilation With Respiratory Extracorporeal Life Support for ARDS

Overview

Acute respiratory distress syndrome (ARDS) accounts for approximately 10% of all ICU admissions and 23% of patients requiring mechanical ventilation (MV). Despite advances in care, hospital mortality remains high, ranging from 34% in mild cases to 46% in severe ARDS. Positive-pressure MV remains the cornerstone of ARDS management. However, when excessive stress and strain are applied to the lung parenchyma, it can exacerbate lung injury, leading to ventilator-induced lung injury (VILI). VILI substantially contributes to morbidity and mortality in ARDS. Strategies that reduce tidal volume (Vt), driving pressure (ΔP, defined as plateau pressure minus PEEP), and respiratory rate (RR) can lower the mechanical power (PowerRS), i.e., the energy delivered to the lungs by the ventilator. This reduction in pulmonary stress and strain may lessen VILI and potentially improve survival. Nonetheless, reducing Vt to \<6 ml/kg in order to achieve plateau pressures \<23-25 cm H₂O, driving pressures \<9-11 cm H₂O, and RR \<15-20/min can result in severe hypercapnia. This, in turn, may increase intracranial pressure, promote pulmonary hypertension, impair myocardial contractility, reduce renal perfusion, and trigger endogenous catecholamine release. Thus, such "ultraprotective" MV strategies are not feasible for most ARDS patients managed with conventional ventilation. The neutral findings of the REST trial further suggested that low-flow extracorporeal CO₂ removal (ECCO₂R) devices may provide insufficient CO₂ clearance to enable ultraprotective ventilation while adequately controlling respiratory acidosis. Moreover, since partial lung derecruitment may occur with substantial Vt reduction, extracorporeal membrane oxygenation (ECMO) may be necessary, particularly in patients with PaO₂/FiO₂ \<120-130 at the time of Vt reduction. Therefore, respiratory extracorporeal life support (ECLS)-ranging from high-flow ECCO₂R to mid-flow venovenous ECMO (VV-ECMO)-can be employed in this setting. These modalities facilitate further reductions in ventilatory intensity while ensuring adequate oxygenation and CO₂ removal.