Acute respiratory distress syndrome
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Definition and Epidemiology of Acute Respiratory Distress Syndrome (ARDS)
Acute respiratory distress syndrome (ARDS) is a severe, life-threatening condition marked by acute respiratory failure, usually triggered by various insults such as pneumonia, sepsis, aspiration, trauma, or blood transfusions Matthay1996Dushianthan2011Xie2025. It is characterized by rapid-onset inflammation in the lungs, increased alveolar and vascular permeability, and the accumulation of protein-rich pulmonary edema, leading to severe hypoxemia and impaired gas exchange Yadam2016Matthay1996Han2015+7 MORE. ARDS is not a single disease but represents the severe end of a spectrum of acute lung injury . The syndrome is common in intensive care units, affecting about 10–20% of critically ill patients, and is associated with high mortality rates, with in-hospital mortality reaching up to 40% Robinson2021Meyer2021Xie2025.
Pathophysiology and Mechanisms of ARDS
The underlying mechanism of ARDS involves inflammatory injury to the alveolar-capillary barrier, resulting in increased permeability and leakage of fluid into the airspaces Yadam2016Matthay1996Han2015+4 MORE. This process is driven by the activation and dysregulation of multiple inflammatory and coagulation pathways, involving neutrophils, platelets, and other immune cells Han2015Xie2025Matthay2011+1 MORE. The resulting damage leads to diffuse alveolar damage, poor lung compliance, and severe hypoxemia Dushianthan2011Xie2025Matthay2011+1 MORE. Genetic and environmental factors may also influence susceptibility and outcomes in ARDS Matthay1996Dushianthan2011.
Diagnosis and Severity Classification
ARDS is diagnosed based on clinical criteria, including acute onset, bilateral chest radiographic opacities, and severe hypoxemia not fully explained by cardiac failure or fluid overload Meyer2021Dushianthan2011. The Berlin definition classifies ARDS severity using the PaO2/FiO2 ratio, which helps guide treatment strategies Yadam2016Meyer2021Koh2014.
Evidence-Based Management and Supportive Therapies
Supportive care remains the cornerstone of ARDS management, as no effective pharmacologic therapy has been established Han2015Meyer2021Dushianthan2011+2 MORE. The most important intervention is lung-protective ventilation using low tidal volumes (6–8 mL/kg of ideal body weight), which has been shown to reduce mortality Yadam2016Matthay1996Meyer2021+3 MORE. Additional strategies that have demonstrated benefit include:
- Prone positioning for severe ARDS, which improves oxygenation Yadam2016Meyer2021Koh2014
- Positive end-expiratory pressure (PEEP) and lung recruitment maneuvers to maintain alveolar patency Yadam2016Koh2014
- Extracorporeal membrane oxygenation (ECMO) for refractory hypoxemia Yadam2016Meyer2021Koh2014
- Judicious fluid management and multi-organ support
Other supportive measures, such as early enteral nutrition, antimicrobial therapy, and prophylaxis against complications, contribute to improved outcomes .
Experimental and Emerging Therapies
Despite extensive research, pharmacologic treatments such as corticosteroids, nitric oxide, prostacyclins, exogenous surfactants, and antioxidants have not shown consistent benefit in human studies Dushianthan2011Matthay2011. Recent trials with β2 agonists and immunonutrition have also been disappointing . However, ongoing research is exploring novel approaches, including cell-based therapies like mesenchymal stem cells, modulation of inflammation, and identification of biomarkers or genetic markers for better diagnosis and personalized treatment Dushianthan2011Matthay2011Huppert2019.
Special Considerations: COVID-19 and ARDS
The COVID-19 pandemic has led to an increase in ARDS cases and highlighted the challenges of high mortality and lack of effective drug therapies Meyer2021Xie2025. While the management principles remain similar, ongoing research is examining the unique features and treatment responses of COVID-19-associated ARDS Meyer2021Xie2025.
Conclusion
ARDS is a complex, multifactorial syndrome with high morbidity and mortality. Advances in supportive care, especially lung-protective ventilation, have improved outcomes, but effective pharmacologic therapies remain elusive. Future research is focused on understanding the underlying mechanisms, identifying biomarkers, and developing targeted treatments to further reduce the burden of this critical illness Han2015Dushianthan2011Xie2025+2 MORE.
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