# Acute Respiratory Distress Syndrome Definitions in Adults and Children: A Comparative Narrative Review

## TL;DR

This paper compares adult and pediatric definitions of Acute Respiratory Distress Syndrome (ARDS) to highlight similarities and differences in diagnosis and implications for patient care.

## Contribution

The paper provides a comparative analysis of the latest global ARDS definitions for adults and children, emphasizing key diagnostic distinctions and their clinical implications.

## Key findings

- Both adult and pediatric ARDS definitions incorporate non-invasive oxygenation indices and adaptability to resource-limited settings.
- Pediatric criteria use Oxygenation Index (OI) or Oxygen Saturation Index (OSI) for ventilated patients, which correlate better with outcomes than PaO2/FIO2.
- Imaging requirements differ, with adult definitions requiring bilateral opacities and pediatric definitions allowing unilateral findings.

## Abstract

Background: Acute Respiratory Distress Syndrome (ARDS) was first described in 1967 by Ashbaugh et al. as a severe acute hypoxemic respiratory failure with reduced lung compliance, representing a common end-path of severe pulmonary endothelial inflammation from diverse etiologies. Since then, several definitions for the adult syndrome have been proposed, culminating in the 2024 “New Global Definition” (Berlin 2.0). In pediatrics, dedicated criteria (pediatric ARDS, PARDS) have been established over the past decade, with the most recent update published by the Second Pediatric Acute Lung Injury Consensus Conference (PALICC-2) in 2023. Methods: We performed a narrative literature review of consensus statements and key studies defining ARDS in adult and pediatric (non-neonatal) populations. Primary sources included the full Berlin 2.0 and PALICC-2 documents, supplemented by PubMed, Embase, and society guidelines. Definitions were compared across major diagnostic domains: timing of onset, imaging requirements, oxygenation thresholds, inclusion of patients with chronic comorbidities, ventilatory support modalities, and applicability in resource-limited settings. Results: Both definitions show convergence in incorporating non-invasive oxygenation indices and adaptability to resource-limited contexts. Key distinctions include the use of the Oxygenation Index (OI) or Oxygen Saturation Index (OSI) in invasively ventilated pediatric patients—metrics that integrate mean airway pressure and correlate more strongly than PaO2/FIO2 with short-term outcomes—and PALICC-2’s explicit inclusion of patients with chronic lung disease or cyanotic congenital heart disease when acute deterioration is documented. Imaging criteria differ, with Berlin 2.0 requiring bilateral opacities (and permitting lung ultrasound) versus PALICC-2’s acceptance of unilateral findings. Conclusions: Berlin 2.0 and PALICC-2 represent substantial progress toward globally applicable ARDS definitions, but physiologic and structural differences remain. These distinctions have prognostic and research implications, and harmonization will be critical to improve cross-age comparability, optimize clinical trial design, and ultimately enhance patient outcomes.