Why use it

The decision to initiate VV-ECMO for refractory respiratory failure is complex, resource-intensive, and carries significant risks. The RESP score provides objective, pre-ECMO prognostic information to guide the decision to initiate ECMO, inform patient and family counseling, assist in triage for ECMO transfer to specialized centers, and benchmark institutional ECMO outcomes for quality improvement. It helps identify patients likely to benefit from ECMO (Class I–II) versus those with very high predicted mortality where ECMO may not improve outcomes without careful patient selection (Class V).

About

The Respiratory ECMO Survival Prediction (RESP) Score was developed by Schmidt and colleagues using data from the Extracorporeal Life Support Organization (ELSO) registry and published in the American Journal of Respiratory and Critical Care Medicine in 2014. It is the most widely used and validated prognostic tool for adults receiving venovenous ECMO (VV-ECMO) for severe acute respiratory failure. The score was derived from 2,355 adult patients in the ELSO registry (2000–2012) who received ECMO for respiratory support, using pre-ECMO variables to predict in-hospital survival. Thirteen pre-ECMO variables are assessed across five domains: age, immunocompromised status, duration of mechanical ventilation before ECMO, primary diagnosis group, associated organ dysfunction (CNS dysfunction and non-pulmonary infections), and physiological parameters (neuromuscular blockade, nitric oxide use, bicarbonate infusion before ECMO, cardiac arrest before ECMO, peak inspiratory pressure, and PaCO2). Total score ranges from −22 to +33; five risk classes are defined with hospital survival rates ranging from 18% (Class V) to 92% (Class I). The RESP score has been externally validated in multiple international ECMO center cohorts and is incorporated into ELSO guidelines and ECMO selection algorithms.

When to use

Adults with severe acute respiratory failure being considered for initiation of venovenous ECMO
Pre-ECMO prognostic assessment for patient and family counseling
Triage of patients for inter-hospital transfer to ECMO-capable centers
Assessment at the time of ECMO cannulation — use pre-ECMO values for all variables
Institutional benchmarking and quality improvement in ECMO programs
NOT for use after ECMO initiation (designed for pre-ECMO assessment only)
NOT validated for venoarterial (VA) ECMO used for cardiac failure — use SAVE score for cardiac ECMO

Formula

RESP Score Variables and Points: Age (years): 18–49: +6 50–59: +5 60–69: +3 ≥70: 0 Immunocompromised status: No: +3 Yes: 0 Mechanical ventilation duration before ECMO: <48 hours: +3 48h – 7 days: +1 ≥7 days: 0 Diagnosis: Viral pneumonia: +3 Bacterial pneumonia: +3 Asthma: +11 Trauma / burn: +3 Aspiration pneumonitis: +5 Other acute respiratory: +1 Nonrespiratory / chronic: 0 CNS dysfunction: None: 0 Present: −7 Acute non-pulmonary infection: No: 0 Yes: −3 Neuromuscular blockade before ECMO: Yes: +1 No: 0 Nitric oxide before ECMO: Yes: −1 No: 0 Bicarbonate infusion before ECMO: Yes: −2 No: 0 Cardiac arrest before ECMO: Yes: −2 No: 0 PaCO2 ≥75 mmHg before ECMO: Yes: +3 No: 0 Peak inspiratory pressure ≤42 cmH2O: Yes: +3 No: 0 Risk Classes (in-hospital survival): Class I (≥6): 92% Class II (3–5): 76% Class III (0–2): 57% Class IV (−4 to −1): 33% Class V (≤−5): 18%

Pearls & pitfalls

All variables should reflect the pre-ECMO status — use values from the 24h before ECMO initiation for physiological parameters and the clinical status at the time of the ECMO decision.
The diagnosis group item is the most heavily weighted positive predictor in the score — asthma (+11) and aspiration pneumonitis (+5) have much better outcomes than nonrespiratory diagnoses (0).
CNS dysfunction carries the highest negative weight (−7 points) — this reflects the devastating impact of concurrent neurological injury on ECMO outcomes, both due to prognosis and the technical challenges of anticoagulation in patients with intracranial pathology.
A cardiac arrest BEFORE ECMO initiation reduces the score by 2 points — this captures the overall severity of physiological derangement before cannulation.
High PaCO2 (≥75 mmHg) and low peak inspiratory pressure (≤42 cmH2O) both contribute positive points — paradoxically, these reflect more conservative ventilation strategies (permissive hypercapnia, low-tidal-volume ventilation) that are associated with better ECMO candidacy.
The RESP score was derived before the widespread adoption of "protective" lung-rest strategies during ECMO — contemporary ECMO outcomes may be better than predicted, particularly in high-volume centers.
For COVID-19-associated ARDS, the RESP score has been applied but with variable predictive accuracy — some studies suggest it may underestimate mortality in COVID-19 ECMO patients.
The RESP score predicts in-hospital survival, not long-term outcomes — ECMO survivors generally have good functional recovery, but 1-year outcomes depend on the underlying disease process.
Use the RESP score as ONE input in a multi-factor decision — clinical gestalt, underlying diagnosis reversibility, ECMO center volume, resource availability, and patient/family goals all matter.
The SAVE score (Survival After Veno-Arterial ECMO) is the analogous tool for VA-ECMO in cardiac failure — do not confuse or interchange these two scores.

Next steps

RESP Class I (≥6 pts, ~92% survival): Excellent prognosis. ECMO strongly supported in eligible patients. Pursue ECMO cannulation if refractory hypoxemia on optimized conventional therapy. RESP Class II (3–5 pts, ~76%): Good prognosis. ECMO is appropriate and expected to be beneficial. Initiate ECMO if conventional therapy fails. RESP Class III (0–2 pts, ~57%): Moderate prognosis. ECMO is reasonable but outcomes are more uncertain. Careful patient selection and goals-of-care discussion recommended. RESP Class IV (−4 to −1 pts, ~33%): Poor prognosis. ECMO carries high mortality risk. Thorough goals-of-care discussion with patient and family is mandatory. ECMO may be considered in carefully selected patients with potentially reversible underlying etiology. RESP Class V (≤−5 pts, ~18%): Very poor prognosis. ECMO is unlikely to improve outcomes. Goals-of-care discussion is mandatory. ECMO may not be the appropriate treatment; comfort-focused care should be discussed.

Evidence

Schmidt M et al. Predicting survival after ECMO for refractory cardiogenic shock: the survival after veno-arterial-ECMO (SAVE)-score. Eur Heart J. 2015. Schmidt M et al. Predicting survival after extracorporeal membrane oxygenation for severe acute respiratory failure. The Respiratory Extracorporeal Membrane Oxygenation Survival Prediction (RESP) score. Am J Respir Crit Care Med. 2014;189(11):1374-1382. PMID:24693768. Derivation: n=2,355 ELSO registry patients (2000–2012). AUC 0.74 for in-hospital survival. Five risk classes with survival 18–92%. External validation: Brunet J et al. Crit Care. 2017; Pappalardo F et al. Crit Care. 2016. AUC in validation cohorts: 0.70–0.78.

References

Schmidt M et al. Predicting survival after extracorporeal membrane oxygenation for severe acute respiratory failure. The Respiratory Extracorporeal Membrane Oxygenation Survival Prediction (RESP) score. Am J Respir Crit Care Med. 2014;189(11):1374-1382. — link
Extracorporeal Life Support Organization (ELSO). ELSO Guidelines for Cardiopulmonary Extracorporeal Life Support. Version 1.4. Ann Arbor, MI: ELSO; 2017. — link
Combes A et al. Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome (EOLIA Trial). N Engl J Med. 2018;378(21):1965-1975. — link
Pappalardo F et al. Predicting mortality risk in patients undergoing venovenous ECMO for ARDS due to influenza A (H1N1) pneumonia: the ECMOnet score. Intensive Care Med. 2013;39(2):275-281. — link
Brunet J et al. Validation of the RESP score in patients with ARDS receiving extracorporeal membrane oxygenation. Crit Care. 2017;21(1):140. — link

RESP (Respiratory ECMO Survival Prediction) Score

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