Limitations of SpO / FiO-ratio for Classification and Monitoring of Acute Respiratory Distress Syndrome-an Observational Cohort Study

Overview

Journal Crit Care

Specialty Critical Care

Date 2025 Feb 19

PMID 39972458

Authors

Rolf Erlebach

Una Pale

Tilman Beck

Sasa Markovic

Marko Seric

Sascha David

Emanuela Keller

Affiliations

Soon will be listed here.

Abstract

Background: The ratio of pulse-oximetric peripheral oxygen saturation to fraction of inspired oxygen (SpO/FiO) has been proposed as additional hypoxemia criterion in a new global definition of acute respiratory distress syndrome (ARDS). This study aims to evaluate the clinical and theoretical limitations of the SpO/FiO-ratio when using it to classify patients with ARDS and to follow disease progression.

Methods: Observational cohort study of ARDS patients from three high-resolution Intensive Care Unit databases, including our own database ICU Cockpit, MIMIC-IV (Version 3.0) and SICdb (Version 1.0.6). Patients with ARDS were identified based on the Berlin criteria or ICD 9/10-codes. Time-matched datapoints of SpO, FiO and partial pressure of oxygen in arterial blood (PaO) were created. Severity classification followed the thresholds for SpO/FiO and PaO/FiO of the newly proposed global definition.

Results: Overall, 708 ARDS patients were included in the analysis. ARDS severity was misclassified by SpO/FiO in 33% of datapoints, out of which 84% were classified as more severe. This can be partially explained by imprecision of SpO measurement and equation used to transform SpO/FiO to PaO/FiO A high dependence of SpO/FiO-ratio on FiO settings was found, leading to major treatment effect and limited capability for tracking change in ARDS severity, which was achieved in less than 20% of events.

Conclusions: The use of SpO/FiO interchangeably with PaO/FiO for severity classification and monitoring of ARDS is limited by its inadequate trending ability and high dependence on FiO settings, which may influence treatment decisions and patient selection in clinical trials.

References

Schjorring O, Klitgaard T, Perner A, Wetterslev J, Lange T, Siegemund M . Lower or Higher Oxygenation Targets for Acute Hypoxemic Respiratory Failure. N Engl J Med. 2021; 384(14):1301-1311. DOI: 10.1056/NEJMoa2032510. View

Schmidt M, Gernand J, Kakarala R . The use of the pulse oximetric saturation to fraction of inspired oxygen ratio in an automated acute respiratory distress syndrome screening tool. J Crit Care. 2015; 30(3):486-90. DOI: 10.1016/j.jcrc.2015.02.007. View

Cane R, Shapiro B, Templin R, Walther K . Unreliability of oxygen tension-based indices in reflecting intrapulmonary shunting in critically ill patients. Crit Care Med. 1988; 16(12):1243-5. DOI: 10.1097/00003246-198812000-00014. View

Girardis M, Busani S, Damiani E, Donati A, Rinaldi L, Marudi A . Effect of Conservative vs Conventional Oxygen Therapy on Mortality Among Patients in an Intensive Care Unit: The Oxygen-ICU Randomized Clinical Trial. JAMA. 2016; 316(15):1583-1589. DOI: 10.1001/jama.2016.11993. View

von Elm E, Altman D, Egger M, Pocock S, Gotzsche P, Vandenbroucke J . The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. Lancet. 2007; 370(9596):1453-7. DOI: 10.1016/S0140-6736(07)61602-X. View

Ranieri V, Tonetti T, Navalesi P, Nava S, Antonelli M, Pesenti A . High-Flow Nasal Oxygen for Severe Hypoxemia: Oxygenation Response and Outcome in Patients with COVID-19. Am J Respir Crit Care Med. 2021; 205(4):431-439. PMC: 8886947. DOI: 10.1164/rccm.202109-2163OC. View

HELMHOLZ Jr H . The abbreviated alveolar air equation. Chest. 1979; 75(6):748. DOI: 10.1378/chest.75.6.748. View

Ranieri V, Rubenfeld G, Thompson B, Ferguson N, Caldwell E, Fan E . Acute respiratory distress syndrome: the Berlin Definition. JAMA. 2012; 307(23):2526-33. DOI: 10.1001/jama.2012.5669. View

Qian F, van den Boom W, See K . The new global definition of acute respiratory distress syndrome: insights from the MIMIC-IV database. Intensive Care Med. 2024; 50(4):608-609. DOI: 10.1007/s00134-024-07383-x. View

10.

Barrot L, Asfar P, Mauny F, Winiszewski H, Montini F, Badie J . Liberal or Conservative Oxygen Therapy for Acute Respiratory Distress Syndrome. N Engl J Med. 2020; 382(11):999-1008. DOI: 10.1056/NEJMoa1916431. View

11.

Mackle D, Bellomo R, Bailey M, Beasley R, Deane A, Eastwood G . Conservative Oxygen Therapy during Mechanical Ventilation in the ICU. N Engl J Med. 2019; 382(11):989-998. DOI: 10.1056/NEJMoa1903297. View

12.

Rodemund N, Wernly B, Jung C, Cozowicz C, Kokofer A . The Salzburg Intensive Care database (SICdb): an openly available critical care dataset. Intensive Care Med. 2023; 49(6):700-702. PMC: 10287776. DOI: 10.1007/s00134-023-07046-3. View

13.

Jubran A . Pulse oximetry. Crit Care. 2015; 19:272. PMC: 4504215. DOI: 10.1186/s13054-015-0984-8. View

14.

Chen W, Janz D, Shaver C, Bernard G, Bastarache J, Ware L . Clinical Characteristics and Outcomes Are Similar in ARDS Diagnosed by Oxygen Saturation/Fio2 Ratio Compared With Pao2/Fio2 Ratio. Chest. 2015; 148(6):1477-1483. PMC: 4665739. DOI: 10.1378/chest.15-0169. View

15.

Brower R, Matthay M, Morris A, Schoenfeld D, Thompson B, Wheeler A . Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000; 342(18):1301-8. DOI: 10.1056/NEJM200005043421801. View

16.

Guerin C, Reignier J, Richard J, Beuret P, Gacouin A, Boulain T . Prone positioning in severe acute respiratory distress syndrome. N Engl J Med. 2013; 368(23):2159-68. DOI: 10.1056/NEJMoa1214103. View

17.

Rice T, Wheeler A, Bernard G, Hayden D, Schoenfeld D, Ware L . Comparison of the SpO2/FIO2 ratio and the PaO2/FIO2 ratio in patients with acute lung injury or ARDS. Chest. 2007; 132(2):410-7. DOI: 10.1378/chest.07-0617. View

18.

Tripathi R, Blum J, Rosenberg A, Tremper K . Pulse oximetry saturation to fraction inspired oxygen ratio as a measure of hypoxia under general anesthesia and the influence of positive end-expiratory pressure. J Crit Care. 2010; 25(3):542.e9-13. DOI: 10.1016/j.jcrc.2010.04.009. View

19.

Jubran . Pulse oximetry. Crit Care. 2000; 3(2):R11-R17. PMC: 137227. DOI: 10.1186/cc341. View

20.

Goldberger A, Amaral L, Glass L, Hausdorff J, Ivanov P, Mark R . PhysioBank, PhysioToolkit, and PhysioNet: components of a new research resource for complex physiologic signals. Circulation. 2000; 101(23):E215-20. DOI: 10.1161/01.cir.101.23.e215. View