New ARDS Definition Expands Global Diagnostic Access

The 2024 Global Definition of Acute Respiratory Distress Syndrome, or ARDS, represents a significant evolution in how this critical lung condition is identified and managed worldwide. Published in Intensive Care Medicine, this editorial by Elisabeth D. Riviello, Lorraine B. Ware, and Michael A. Matthay outlines the historical trajectory of ARDS definitions and explains how the latest update aims to ensure equitable clinical care and research participation across diverse global settings. The new definition expands upon the 2012 Berlin definition by including patients with severe hypoxemia who are not intubated, thereby broadening the scope of diagnosis beyond the traditional intensive care unit environment.

ARDS was first described sixty years ago in a case series of patients experiencing acute respiratory failure due to non-cardiogenic pulmonary edema. Since that initial description, the definition of the syndrome has evolved through several discrete steps, with each revision enabling advancements in both clinical care and research. The most recent update is designed to address the limitations of previous definitions, which often relied on resources and technologies not available in many parts of the world. By incorporating more accessible diagnostic tools, the 2024 definition seeks to legitimize the diagnosis of ARDS in resource-constrained settings where modern intensive care infrastructure is scarce.

The history of defining ARDS is marked by a gradual expansion of criteria to capture the syndromic nature of the condition more accurately. In 1967, Ashbaugh and colleagues first described ARDS in twelve patients, noting a condition manifested by the acute onset of tachypnea, hypoxemia, and loss of compliance that did not respond to standard respiratory therapy. Earlier, during World War II, the “wet lung of trauma” described by Lyman Brewer provided the first detailed account of the non-cardiogenic and often-fatal pulmonary edema associated with ARDS, although this was limited to a specific subset of trauma patients.

In 1988, Murray and colleagues created a definition that classified ARDS based on the severity of hypoxemia, the level of positive end-expiratory pressure, static lung compliance, and the extent of chest radiograph opacities. This was followed in 1994 by the American-European consensus conference, which operationalized the definitions of Acute Lung Injury and ARDS with specific criteria. These included acute onset, hypoxemia with a PaO2/FiO2 ratio of less than or equal to 300 mmHg for Acute Lung Injury and less than or equal to 200 mmHg for ARDS, bilateral opacities on chest radiograph, and a pulmonary artery wedge pressure of less than or equal to 18 mmHg or no clinical evidence of left atrial hypertension.

The 1994 definition served as the basis for major clinical trials, including the lung protective ventilation trial and the Fluid and Catheter Treatment Trials, both of which transformed clinical care for ARDS. In 2012, the Berlin definition further refined the criteria by including all patients with a PaO2/FiO2 ratio of less than or equal to 300 as ARDS, categorizing them into mild, moderate, and severe groups. It also added a requirement for positive end-expiratory pressure of at least 5 cmH2O, included computed tomography as a reasonable imaging modality, and changed the requirement for normal left atrial pressures to a statement that hydrostatic edema is not the primary cause of respiratory failure.

An editorial by Derek Angus noted that the PEEP requirement had essentially excluded ARDS as a possible diagnosis in patients without ventilation, highlighting a significant gap in global applicability. This critique underscored the fact that many individuals worldwide develop critical illness far from modern intensive care units, where such equipment may not be available.

In 2016, the Kigali modification of the Berlin definition addressed the scarcity of ventilators, arterial blood gases, and chest radiography in resource-constrained areas. This modification paved the way for the 2024 Global Definition, which provides three distinct pathways to an ARDS diagnosis: for patients who are ventilated, for patients on high-flow oxygen, and for patients in resource-constrained settings. This expanded definition incorporates more widely available diagnostic modalities, including lung ultrasound and pulse oximetry, and includes categories for which positive end-expiratory pressure is not required. It also acknowledges the increasing use of high-flow oxygen in very hypoxemic patients, allowing for earlier recognition and enrollment in clinical trials.

The 2024 Global Definition represents a return to the original observations and limited resources of the initial descriptions of ARDS in the 1940s and 1967. By establishing and legitimizing a definition that can be used in resource-constrained settings, the new criteria act as a catalyst for equity in global health. Since 87% of the world’s population lives outside high-income countries, and the vast majority of ARDS studies are conducted in these high-income settings, this move toward equity is critical. The inclusion of pulse oximetry as a diagnostic tool increases accessibility by allowing for an inexpensive and non-invasive measurement of hypoxemia, although it is also recognized as a source of inequity due to increased inaccuracy in patients with darker skin tones and those in shock.

Additionally, the Global Definition acknowledges and builds on developments in high-income country clinical practice. A recent trial demonstrated that deferring or avoiding arterial lines for blood gases is non-inferior to early placement, supporting the use of less invasive monitoring. Ultrasound is also highlighted as a non-invasive bedside method for assessing pulmonary edema, a technique that is increasing in both high-resource and low-resource settings. By including patients on high-flow oxygen, the definition allows for earlier recognition of ARDS, as many severely hypoxemic patients are managed with this therapy prior to intubation or as definitive treatment.

This editorial, Part 1 of a two-part series, presents a brief history of ARDS definitions to contextualize the 2024 update. Part 2 will discuss the importance of a globally accessible definition and present future directions for defining ARDS, including the potential inclusion of subphenotypes, mechanisms, biomarkers, and treatable traits. The authors emphasize that the definition of ARDS is likely to continue to evolve given its syndromic quality.

The 2024 Global Definition lays the groundwork for future updates that may incorporate new insights into the pathophysiology of ARDS, including the role of biomarkers and subphenotypes.

Subject of Research: Evolution of Acute Respiratory Distress Syndrome definitions and the 2024 Global Definition's impact on global diagnostic equity.

Article Title: Defining ARDS: Globalization and personalization to better serve the World – Part 1

Article References: Riviello, E. D., Ware, L. B., & Matthay, M. A. (2026). Defining ARDS: Globalization and personalization to better serve the World – Part 1. Intensive Care Medicine. https://doi.org/10.1007/s00134-026-08651-8

Image Credits: AI Generated

DOI: 10.1007/s00134-026-08651-8

Keywords: ARDS, Intensive Care Medicine, Global Health, Diagnostic Criteria, Pulse Oximetry, Lung Ultrasound, Berlin Definition, Clinical Research, Respiratory Failure, Health Equity, Defining, Globalization