Extracorporeal life support for adults with acute respiratory distress syndrome

Abstract

Extracorporeal life support (ECLS) can support gas exchange in patients with the acute respiratory distress syndrome (ARDS). During ECLS, venous blood is drained from a central vein via a cannula, pumped through a semipermeable membrane that permits diffusion of oxygen and carbon dioxide, and returned via a cannula to a central vein. Two related forms of ECLS are used. Venovenous extracorporeal membrane oxygenation (ECMO), which uses high blood flow rates to both oxygenate the blood and remove carbon dioxide, may be considered in patients with severe ARDS whose oxygenation or ventilation cannot be maintained adequately with best practice conventional mechanical ventilation and adjunctive therapies, including prone positioning. Extracorporeal carbon dioxide removal (ECCO₂R) uses lower blood flow rates through smaller cannulae and provides substantial CO₂ elimination (~ 20-70% of total CO₂ production), albeit with marginal improvement in oxygenation. The rationale for using ECCO₂R in ARDS is to facilitate lung-protective ventilation by allowing a reduction of tidal volume, respiratory rate, plateau pressure, driving pressure and mechanical power delivered by the mechanical ventilator. This narrative review summarizes physiological concepts related to ECLS, as well as the rationale and evidence supporting ECMO and ECCO₂R for the treatment of ARDS. It also reviews complications, limitations, and the ethical dilemmas that can arise in treating patients with ECLS. Finally, it discusses future key research questions and challenges for this technology.

Keywords: Acute respiratory failure; Extracorporeal membrane oxygenation; Mechanical ventilation; Outcome.

Fig. 1

Three different modalities of ECLS for acute respiratory distress syndrome. A Femoro-jugular venovenous extracorporeal membrane oxygenation (VV-ECMO) which enables full oxygenation and carbon dioxide removal in the acute phase of ARDS. Typical mechanical ventilation settings (EOLIA settings) aim to further protect the lung by reducing VT, RR, and ∆P; B Dual-lumen jugular VV-ECMO is an alternative cannulation strategy; C Extra-corporeal CO₂ removal, which may facilitate lung-protective ventilation by allowing a reduction of VT, Pplat, RR, ∆P and mechanical power (SUPERNOVA pilot settings) by ensuring partial carbon dioxide removal with marginal oxygenation in mild-to-moderate ARDS. VCV volume-controlled ventilation, PEEP positive end-expiratory pressure, VT tidal volume, Pplat plateau pressure, BIPAP/APRV biphasic positive airway pressure/airway pressure release ventilation, RR respiratory rate, ∆P driving pressure, Fr French, ARDS acute respiratory distress syndrome, ECLS extracorporeal life support, MV mechanical ventilation, FdO₂ fraction on oxygen in the sweep gas, MO, membrane oxygenator, Qecmo (Q_E) ECMO flow in L/min. Major changes between the three settings are highlighted in bold font. ^a Modified EOLIA settings with a set RR lower than in EOLIA. Decreasing respiratory rate (< 10–15 breaths/min) to reduce mechanical power seems desirable, although it may be achieved in most ARDS patients only with deep sedation and neuromuscular blockade

Fig. 2

VV-ECMO weaning algorithm in severe acute respiratory distress syndrome. VV-ECMO venovenous extracorporeal membrane oxygenation, VCV volume-controlled ventilation, PEEP positive end-expiratory pressure, VT tidal volume, P_plat plateau pressure, BIPAP/APRV biphasic positive airway pressure/airway pressure release ventilation, P_high high pressure, P_low low pressure, RR respiratory rate, MV mechanical ventilation, F_dO₂ fraction on oxygen in the sweep gas, PBW predicted body weight, H hour. ^a Modified EOLIA settings with a set RR lower than in EOLIA. Decreasing respiratory rate (< 10–15 breaths/min) to reduce mechanical power seems desirable, although it may be achieved in most ARDS patients only with deep sedation and neuromuscular blockade

Fig. 3

Clinical management and daily monitoring of ECMO for ARDS. VV-ECMO venovenous extracorporeal membrane oxygenation, VCV volume-controlled ventilation, PEEP positive end-expiratory pressure, VT tidal volume, P_plat plateau pressure, RR respiratory rate, ∆P driving pressure, BIPAP/APRV biphasic positive airway pressure/airway pressure release ventilation, P_high high pressure, P_low low pressure, UFH Unfractionated heparin, aPTT activated partial thromboplastin time, PK/PD pharmacokinetic/pharmacodynamics, RASS richmond agitation-sedation scale, P_0.1 drop in airway pressure observed during the first 100 ms of an inspiratory effort made against the occluded airway opening, Pven venous pressure (i.e. inlet pressure) on ECMO, Part arterial pressure (i.e., outlet pressure) on ECMO, ∆P on ECMO trans-membrane oxygenator pressure gradient or pressure drop, i.e., the difference betweenthe pressure of the blood at the inlet and at the outlet of the membrane lung, usually 10–50 mmHg. ^a Modified EOLIA settings with a set RR lower than in EOLIA