Pneumonia-driven ARDS: systemic injury, biological subphenotypes, and therapeutic implications

Despite advances in supportive care, acute respiratory distress syndrome (ARDS) precipitated by pneumonia remains associated with high mortality, prolonged mechanical ventilation, and long-term functional impairment. A persistent limitation of current ICU practice is the uniform application of management strategies to biologically heterogeneous forms of ARDS. Pneumonia, the leading precipitating cause, is characterized by ongoing pathogen burden, sustained innate immune activation, endothelial dysfunction, and marked regional heterogeneity, all of which shape physiological derangement and therapeutic responsiveness.

This narrative review integrates experimental, translational, and clinical evidence examining the mechanisms underlying pneumonia-driven ARDS. Particular focus was placed on host–pathogen interactions, alveolar–capillary barrier failure, immune dysregulation, ventilatory inefficiency, biological subphenotypes, temporal evolution of lung injury, and implications for ventilatory and pharmacologic management.

In pneumonia-driven ARDS, early disruption of the alveolar–capillary barrier, neutrophil-mediated epithelial injury, and endothelial dysfunction promote progression from focal infection to diffuse lung injury. The resulting permeability edema, microvascular dysfunction, and increased physiological dead space generate severe ventilation–perfusion mismatch and impaired carbon dioxide clearance, contributing to refractory hypoxemia and variable responses to positive end-expiratory pressure. Mechanical ventilation interacts bidirectionally with this inflammatory milieu, as regional overdistension and cyclic collapse amplify inflammatory signaling and propagate ventilator-induced lung injury in heterogeneous lungs. Infection-driven ARDS frequently exhibits hyperinflammatory subphenotypes characterized by endothelial injury, elevated inflammatory mediators, greater vasopressor requirements, prolonged organ support, and increased mortality. Disease progression from early infectious injury toward fibroproliferation further suggests that therapeutic responsiveness varies across temporal stages of lung injury. Emerging evidence supports the integration of pathogen characteristics, host-response biomarkers, and physiological parameters to improve risk stratification and identify patients more likely to benefit from individualized ventilatory, antimicrobial, fluid, and immunomodulatory strategies.

Pneumonia-driven ARDS represents a clinically relevant biological context of respiratory failure characterized by persistent host–pathogen interactions, dynamic inflammatory responses, and marked physiological heterogeneity. Moving beyond uniform supportive management toward etiology- and subphenotype-informed care may improve treatment selection, optimize organ support, and reduce mortality and long-term disability in ARDS.