**1. Introduction**

Since the 1950s, extracorporeal lung support has experienced continuous advancements in technology and a better understanding of ECMO physiology, which has led to less morbidity and more liberal use of this technology in acute respiratory failure (ARF). Experiences in selecting and managing patients with acute cardiac and respiratory failure treated with ECMO continue to grow. ECMO is a resource-intense

form of lung support that requires significant institutional commitments and a welltrained team to ensure good outcomes.

There are clear benefits of ECMO in patients with acute respiratory failure such as acute respiratory distress syndrome (ARDS), hypercapneic respiratory failure related to infections or flare of their underlying disease, and pulmonary arterial hypertension (PAH) patients with decompensated right heart failure as a bridge-to-recovery (BTR), and as a bridge-to-decision (BTD) for lung transplant candidates, who have not completed the lung transplant evaluation, and as a bridge-to-transplant (BTT) for decompensated lung transplant candidates, hoping to avoid mechanical ventilation, sedation, and the use of neuromuscular blocking agents for conditioning, preservation of lung transplant candidacy, and ultimately better long-term outcomes. However, the decision to support patients with acute or acute-on-chronic respiratory failure with ECMO is challenging. No single guideline exists to aid decision-making, and the clinical management decisions are highly center-specific.

Based on the organ procurement and transplantation network (OPTN)/and the scientific registry of transplant recipient database (SRTR) 2020 report, lung transplant candidates hospitalized in the intensive care unit (ICU) comprised 13.8% of transplant recipients; 9.2% were hospitalized but not in the ICU. Also, candidates continued to be bridged-to-transplant; 3.6% on mechanical ventilation and ECMO, 1.8% on mechanical ventilation only, and 3.1% ECMO only [1].

This chapter will review the ECMO support as a BTR and as a BTD in patients with advanced lung disease and respiratory failure not listed for a lung transplant, including the limited data and the lack of good guidelines on candidate selection and the need for advance care planning, early palliative care involvement, and the need to involve patient and family on the implications of ECMO withdrawn when not a candidate for lung transplantation before deciding to accept ECMO as a bridge-to-decision.
