A new article proposes a novel conceptual framework to guide the management of patients undergoing prolonged veno-venous extracorporeal membrane oxygenation (V-V ECMO) for severe respiratory failure. V-V ECMO is an invasive, resource-intensive therapy used in cases of refractory hypoxaemic respiratory failure, particularly acute respiratory distress syndrome (ARDS), either as a bridge to recovery or transplantation. While substantial literature exists on ECMO initiation and final liberation, there is a notable lack of structured guidance for the prolonged middle phase of care, where complex decisions regarding ventilation, sedation, and weaning must be made. The authors address this gap by dividing prolonged V-V ECMO support into six distinct phases, each with specific clinical priorities and challenges.
Prolonged ECMO is typically defined as support exceeding 14 or 21 days, with survival rates of approximately 45%. The central challenge during this period is balancing the risks of ventilator-induced lung injury (VILI) from premature weaning against the complications of prolonged ECMO, including infection, anticoagulation-related issues, sedation, immobility, and resource burden. Current practice is highly variable across clinicians and institutions, reflecting the absence of evidence-based protocols.
The first phase, ultra-lung-protective ventilation, begins immediately after ECMO initiation. The priority is minimising further lung injury by reducing mechanical power delivered to the lungs. This is achieved through low driving pressures, moderate positive end-expiratory pressure (PEEP), and very low tidal volumes, often between 0–4 mL/kg. In extreme cases, apnoeic ventilation may be used, with gas exchange fully supported by ECMO. Careful adjustment of sweep gas flow (SGF) is essential to avoid rapid reductions in carbon dioxide, which may lead to neurological complications. This phase also contributes to improved right ventricular function by reducing pulmonary pressures. However, the optimal duration of strict lung rest remains uncertain.
The second phase, lung-protective ventilation, begins as pulmonary function improves. Indicators include better oxygenation, enhanced compliance, and radiological improvement. Ventilation is cautiously adjusted to maintain tidal volumes below 6 mL/kg and minimise driving pressure. Transition from pressure-controlled to volume-controlled ventilation may occur to avoid inadvertent overdistension. This phase is highly variable in duration and may be prolonged by complications such as infection or pneumothorax. A key clinical question at this stage is when to initiate spontaneous breathing.
The third phase, transition to spontaneous breathing, represents a critical and complex period. As lung function improves further, ECMO support is gradually reduced and sedation is lightened to allow patient-initiated breathing. However, this introduces the risk of patient self-induced lung injury (P-SILI), caused by excessive inspiratory effort and high transpulmonary pressures. Clinicians must carefully balance sedation and respiratory drive, monitoring for signs of distress and excessive work of breathing. If instability occurs, patients may need to revert to controlled ventilation. This phase also introduces considerations such as tracheostomy, mobilisation, and even extubation while still on ECMO in selected patients.
The fourth phase, liberation trial, involves assessing whether the patient can sustain adequate gas exchange without ECMO support. This typically includes reducing or stopping SGF and observing physiological responses such as oxygenation, carbon dioxide clearance, and work of breathing. Trials may be clinician-guided or protocolised, with the latter associated with shorter ECMO duration. Dead space ventilation, reflecting inefficient gas exchange, is an important predictor of success and may be estimated using the ratio of end-tidal to arterial CO₂.
The fifth phase, decannulation, follows a successful liberation trial. This involves removal of ECMO cannulas under controlled conditions. Key considerations include ensuring adequate ventilation on conventional support, managing anticoagulation, preventing infection, and maintaining haemostasis. The procedure often requires sedation and careful post-procedural monitoring to avoid complications such as bleeding.
The final phase, post-decannulation, resembles recovery from severe ARDS. Patients remain at risk of deterioration and may require re-cannulation. Ongoing lung-protective ventilation strategies are employed, although optimal management is not well defined. Some patients may experience complications such as infection or increased metabolic demand, which can challenge recovery. Notably, repeat ECMO runs are becoming more common, with reported survival exceeding 50% in selected patients.
This framework provides a structured approach to understanding prolonged V-V ECMO management by defining six sequential phases. It emphasises the evolving priorities from lung protection to eventual liberation and recovery, while underscoring the need for individualised, physiology-driven care. The model also identifies critical areas for future research, particularly the need for standardised definitions, protocols, and patient-centred outcomes to improve consistency and optimise care in this complex patient population.
Source: Critical Care
Image Credit: iStock
