BACKGROUND: Extracorporeal membrane oxygenation (ECMO) is a form of life support 
that targets the heart and lungs. Extracorporeal membrane oxygenation for severe 
respiratory failure accesses and returns blood from the venous system and 
provides non-pulmonary gas exchange. Extracorporeal membrane oxygenation for 
severe cardiac failure or for refractory cardiac arrest (extracorporeal 
cardiopulmonary resuscitation (ECPR)) provides gas exchange and systemic 
circulation. The configuration of ECMO is variable, and several pump-driven and 
pump-free systems are in use. Use of ECMO is associated with several risks. 
Patient-related adverse events include haemorrhage or extremity ischaemia; 
circuit-related adverse effects may include pump failure, oxygenator failure and 
thrombus formation. Use of ECMO in newborns and infants is well established, yet 
its clinical effectiveness in adults remains uncertain.
OBJECTIVES: The primary objective of this systematic review was to determine 
whether use of veno-venous (VV) or venous-arterial (VA) ECMO in adults is more 
effective in improving survival compared with conventional respiratory and 
cardiac support.
SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials 
(CENTRAL), MEDLINE (Ovid) and EMBASE (Ovid) on 18 August 2014. We searched 
conference proceedings, meeting abstracts, reference lists of retrieved articles 
and databases of ongoing trials and contacted experts in the field. We imposed 
no restrictions on language or location of publications.
SELECTION CRITERIA: We included randomized controlled trials (RCTs), quasi-RCTs 
and cluster-RCTs that compared adult ECMO versus conventional support.
DATA COLLECTION AND ANALYSIS: Two review authors independently screened the 
titles and abstracts of all retrieved citations against the inclusion criteria. 
We independently reviewed full-text copies of studies that met the inclusion 
criteria. We entered all data extracted from the included studies into Review 
Manager. Two review authors independently performed risk of bias assessment. All 
included studies were appraised with respect to random sequence generation, 
concealment of allocation, blinding of outcome assessment, incomplete outcome 
data, selective reporting and other bias.
MAIN RESULTS: We included four RCTs that randomly assigned 389 participants with 
acute respiratory failure. Risk of bias was low in three RCTs and high in one 
RCT. We found no statistically significant differences in all-cause mortality at 
six months (two RCTs) or before six months (during 30 days of randomization in 
one trial and during hospital stay in another RCT). The quality of the evidence 
was low to moderate, and further research is very likely to impact our 
confidence in the estimate of effects because significant changes have been 
noted in ECMO applications and treatment modalities over study periods to the 
present.Two RCTs supplied data on disability. In one RCT survival was low in 
both groups but none of the survivors had limitations in their daily activities 
six months after discharge. The other RCT reported improved survival without 
severe disability in the intervention group (transfer to an ECMO centre ± ECMO) 
six months after study randomization but no statistically significant 
differences in health-related quality of life.In three RCTs, participants in the 
ECMO group received greater numbers of blood transfusions. One RCT recorded 
significantly more non-brain haemorrhage in the ECMO group. Another RCT reported 
two serious adverse events in the ECMO group, and another reported three adverse 
events in the ECMO group.Clinical heterogeneity between studies prevented 
meta-analyses across outcomes. We found no completed RCT that had investigated 
ECMO in the context of cardiac failure or arrest. We found one ongoing RCT that 
examined patients with acute respiratory failure and two ongoing RCTs that 
included patients with acute cardiac failure (arrest).
AUTHORS' CONCLUSIONS: Extracorporeal membrane oxygenation remains a rescue 
therapy. Since the year 2000, patient treatment and practice with ECMO have 
considerably changed as the result of research findings and technological 
advancements over time. Over the past four decades, only four RCTs have been 
published that compared the intervention versus conventional treatment at the 
time of the study. Clinical heterogeneity across these published studies 
prevented pooling of data for a meta-analysis.We recommend combining results of 
ongoing RCTs with results of trials conducted after the year 2000 if no 
significant shifts in technology or treatment occur. Until these new results 
become available, data on use of ECMO in patients with acute respiratory failure 
remain inconclusive. For patients with acute cardiac failure or arrest, outcomes 
of ongoing RCTs will assist clinicians in determining what role ECMO and ECPR 
can play in patient care.