CHAPTER 53: Extracorporeal Lung Support

KEY POINTS

• Extracorporeal membrane oxygenation (ECMO) can be used to provide support to selected patients with severe acute respiratory failure and severe hypoxemia.

• The two major ECMO modalities are veno-venous (VV) and veno-arterial (VA), but most cases of extracorporeal lung support use VV-ECMO.

• The prospective, randomized Adult ECMO study (CESAR trial) reported a 31% improved outcome in patients transported to a specialized center for possible ECMO (63% vs 47% survival without disability; relative risk 6-month death or severe disability 0.69, 95% CI 0.05-0.97; RR death 0.73, 95% CI 0.52-1.03).

• Significant adverse events and complications can occur during ECMO, most related to hemorrhage, but are becoming less common with improved technology and reduced anticoagulation requirements.

• ECMO is used in patients with severe hypoxemia related to ARDS, 2009 Influenza A (H1N1)–associated ARDS, trauma, and pulmonary embolus.

• Survival to discharge in adult patients receiving ECMO for respiratory failure is 52% from the Extracorporeal Life Support Organization (ELSO) registry.

• VV-ECMO is now being used as a therapeutic option to bridge patients with advanced lung disease to lung transplantation, avoiding the use of mechanical ventilation and allowing aggressive physical rehabilitation.

• A new adult ARDS ECMO multicenter clinical trial has been initiated, entitled ECM O to rescue Lung Injury in severe ARDS (EOLIA, Alain Combes MD, Principal Investigator, France).

• ECMO is a complex critical care organ support system, and requires an experienced and dedicated team, appropriate equipment, and institutional commitment and leadership.

• The current evidence supports the transfer of patients with severe hypoxemia and ARDS to institutions with significant experience in ARDS management and with ECMO capabilities.

EXTRACORPOREAL LUNG SUPPORT

Extracorporeal membrane oxygenation (ECMO) is an advanced treatment option for patients with severe respiratory failure and severe hypoxemia.^1-6 The goal of ECMO for lung support is to avoid the use of high levels of oxygen and high airway pressures that may be necessary to support oxygenation and ventilation with mechanical ventilation in severe hypoxemia and acute respiratory failure. Nearly 20% of acute respiratory distress syndrome (ARDS) patients die of severe hypoxemia.⁷

ARDS is associated with pathologically complex changes in the lung manifested by an early exudative phase followed by proliferative and fibrotic phases.⁸ The acute inflammatory state leads to increased capillary permeability and accumulation of proteinaceous pulmonary edema, leading to hypoxemia. Hypoxia may further aggravate lung injury, and treatment strategies therefore focus on improvement of oxygenation and correction of the underlying problem.⁹

Mechanical ventilatory support can be injurious and lead to additional lung injury when used at the extremes of pulmonary physiology, a concept that has been termed ventilator-induced lung injury (VILI).¹⁰ There are a number of mechanisms that can lead to the development of VILI, including barotrauma, diffuse alveolar injury due to overdistension (volutrauma), injury due to repeated cycles of recruitment/derecruitment (atelectrauma) and the most subtle form of injury due to the release of ...