Table 2 Eligibility criteria and method of quality appraisal or risk of bias of the included SRs

Munshi, 2019 [31]

① RCT and observational study; ② Refractory hypoxia in adults with ARDS (including treatments such as inhaled nitric oxide or highfrequency oscillation); ③ MV plus venovenous (VV) ECMO compared with conventional MV; ④ Reported mortality at any time

Main focused venoarterial (VA) ECMO studies

The cochrane risk­of­bias (ROB) tool and Newcastle­Ottawa Scale (NOS)

Shrestha, 2022 [38]

① Prospective as well as retrospective observational studies and randomized clinical trials; ② Published after 2000; ③ ARDS patients > 18 years of age; ④ Interventions included ECMO (VV/VA or veno arteriovenous (VAV) compared with conventional treatment of MV or other adjunctive therapies; ⑤ Outcomes involving the mortality rate, clinical improvement and recovery, length of hospital stay, adverse effects of ECMO, mean difference of clinical improvement, and healing

① Comments, editorials, viewpoint articles, systematic reviews, or meta-analyses; ② Non-ARDS patients, less than 18 years of age, or pregnant patients; ③ ECMO used for the management of cases other than ARDS; ④ Not mentioned our outcome of interest

The Cochrane ROB 2.0 tool and the Joanna Briggs Institute (JBI) quality assessment tools

Tillmann, 2017 [27]

① Patients > 16 years with severe ARDS as per the Berlin criteria, or classified as having ARDS as per the 1994 American-European Consensus Conference Definition with a PaO2:FiO2 ratio < 100; ② Intervention group received ECMO; ③ Treatment with low tidal volume MV of 8 cm³/kg or less; ④ Reported survival to hospital or ICU discharge

Used ECMO as a pre-specified bridge to lung transplantation

NOS

Mendes Pedro Vitale, 2019 [30]

① RCT; ② Adult patients with ARDS; ③ Used ECMO support plus protective MV compared with protective MV alone

Neonatal, pediatric, and experimental data, as well as case series, observational trials and case reports

The Cochrane ROB tool

Alain Combes, 2020 [32]

① RCT; ② Published after 2000; ③ Patients with ARDS fulfilling the American-European Consensus Conference definition or the Berlin definition for ARDS; ④ VV ECMO in the experimental group and conventional ventilatory management in the control group

Not mentioned

The Cochrane ROB tool

Zhu, 2021 [36]

① Randomized and observational studies; ② Adult populations (age ≥ 18 years old); ③ Comparing ECMO therapy with MV alone in the treatment of severe ARDS; ④ Reported mortality outcomes

① Animal studies or case reports; ② lacked a comparison group; ③ included patients < 18 years

Modified Jadad scores, the Cochrane ROB tool, or NOS

Munshi, 2014 [24]

① ARF patients older than 1 month of age; ② Received ECLS; ③ Compared with patients receiving MV; ④ Reported mortality as an outcome

Not mentioned

The Cochrane ROB tool

Mitchell, 2010 [22]

① Controlled trials or cohort studies; ② Reported on the use of ECMO in influenza patients; ③ Included a minimum of 10 patients in each group; ④ Reported comparisons between patients with ARF managed with and without ECMO; ⑤ Reported mortality rates

Neonatal and pediatric studies (patients under 18 years of age)

A nine-point scale combining elements from Jadad’s and Chalmers’ scales

Alberto Zangrillo, 2013 [23]

① Reported on 10 or more patients; ② With confirmed or suspected H1N1 influenza infection; ③ Receiving ECMO

① Reported on fewer than 10 patients treated with ECMO; ② Duplicate publication

NOS

Alshamsi Fayez, 2020 [34]

① RCT; ② Adults with ALF or ACLF; ③ Intervention with any form of artificial or bio-artificial ECLS; ④ Control group received supportive care not including ECLS; ⑤ All-cause mortality or liver-related mortality, bridging to liver transplant, improvement of HE and adverse events such as hypotension, bleeding, thrombocytopenia, line infection, and citrate toxicity as outcomes

Not mentioned

The Cochrane ROB tool

Ouweneel Dagmar, 2016 [26]

① Diagnosed with either refractory in-hospital or out-of-hospital cardiac arrest or cardiogenic shock after AMI; ② Patients with ECLS support and a control group without ECLS support

① Case reports, non-human studies, pediatric studies, and reviews; ② not reported on survival to discharge, 30-day outcome or 6-month outcome

A modified version of NOS

Beyea, 2018 [28]

① Documented OHCA in adults (age ≥ 16 years); ② Used “ECPR” or equivalent search term, as the intervention; ③ Had either CCPR, defined as either basic life support or advanced cardiovascular life support protocols, or no comparator; ④ Reported hospital outcomes

① Under age 16 years; ② Cardiac arrests of traumatic etiology, or patients suffered in-hospital cardiac arrest including in the emergency department

NOS

Twohig, 2019 [29]

① Observational studies; ② Human adult participants (≥ 17 years old); ③ VA ECMO initiated during cardiac arrest (ECPR);

④ Minimal data outcome of 30-day/hospital mortality reported

① Languages other than English; ② Traumatic cardiac arrest; ③ Comparator not CCPR (only for ECPR vs. CCPR papers); ④ Minimal data outcome not reported or reported at other later time intervals

The Risk of Bias in Non-randomized Studies of Interventions (ROBINS-I) tool

Miraglia, 2020 [33]

① Published in English as full-text articles in indexed journals; ② Used propensity score-matched analysis as part of the study design; ③ Adult participants (≥ 18 years old); ④ Resuscitated from in- and out-of-hospital cardiac arrest; ⑤ Received ECPR; ⑥ Reported neurological outcomes

① Review articles, opinions, letters, case reports, case series, meta-analyses, and studies reported insufficient data; ② Conducted on pregnancy, pediatric populations, presumed pregnancy, or patients with a pulse (eg, cardiogenic shock)

NOS

Miraglia, 2020 [35]

① Employing patient-level randomization or cluster randomization comparing ECPR vs. no ECPR and/or conventional CPR; ② Adults suffering in- or out-of- hospital cardiac arrest, with resuscitation attempted by a bystander or healthcare provider; ③ Compared ECMO using pump-driven VA circuits vs. no ECPR and/or conventional CPR; ④ Long-term neurologically intact survival after in- and out-of- hospital cardiac arrest as the primary outcomes of interest

① Considering in- or out-of- hospital cardiac arrest in pediatrics and pregnancy; ② considering in- or out-of- hospital cardiac arrest due to trauma, hypothermia, and toxic substances, as the core interventions provided by healthcare providers (CPR and early defibrillation)

ROBINS-I tool

Scquizzato, 2022 [37]

① Randomized trials and observational studies reporting propensity score-matched data; ② Comparing adult out-of- hospital cardiac arrest patients treated with ECPR with patients treated with CCPR (i.e., basic and advanced life-support maneuvers)

① Feasibility studies; ② Enrolling less than 20 patients; ③ Not reporting the primary outcome of survival with favorable neurological outcome

The Cochrane ROB 2.0 tool

Ahn Chiwon, 2016 [25]

① Adult patients of cardiac-origin arrest (age 18–75 years); ② Does cardiopulmonary resuscitation with ECMO; ③ Compared to conventional cardiopulmonary resuscitation; ④ Survival rate and neurological outcome as outcomes

① Comments, reviews, case reports, editorials, letters, conference abstracts, meta-analyses, or animal studies; ② Languages other than English; ③ Duplicate studies; ④ Irrelevant populations; ⑤ Inappropriate controls

The Cochrane ROB tool