How I wean patients from veno-venous extra-corporeal membrane oxygenation

Abstract

Identifying patients who are ready for weaning and liberation from veno-venous extracorporeal membrane oxygenation (ECMO) is challenging in clinical practice. Compared to the several trials addressing the safety and efficacy of ECMO in severe ARDS [1–4], the body of literature regarding ECMO weaning is remarkably scarce. Therefore, this essential component of the management of patients on ECMO is highly variable and often lacks of a systematic approach [5], analogously to the weaning protocols and spontaneous breathing trials used for liberation from mechanical ventilation [6]. The trajectory from ECMO cannulation to lung recovery and ECMO decannulation consists in the transition from a phase in which ECMO is essential to meet the patient’s metabolic needs (i.e. metabolic oxygen consumption and CO2 production) to a phase in which the native lung function has recovered to satisfy completely the metabolic demands, even if with a degree of ventilatory support considered “safe”. In between these two phases is a continuum of lung healing, during which lung function becomes sufficient to maintain a gas exchange compatible with life, but at the expenses of a high respiratory drive and large swings in transpulmonary pressures. In these conditions, ECMO has the role of maintaining lung protection partially contributing to the patient’s gas exchange [5]. In the effort to track the progress of an individual patient along this imaginary line, it is necessary to measure the relative contribution of the membrane and native lungs in terms of gas exchange, as well as the response of the patient’s respiratory drive and mechanics to the variation in ECMO settings. We propose a physiology-based assessment protocol, which combines an objective assessment of the native and artificial lung function and quantifies the patient’s response to a standardised weaning trial.