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Acute Respiratory Distress Syndrome

Q: What are the main synonyms for acute respiratory distress syndrome in adults?

The disease is referred to as non-cardiogenic pulmonary edema, as well as "wet", "heavy", "shock", or "moist" lung.

Q: Are there signs of primary heart failure in the initial stage?

No, in the initial stage of the syndrome, signs of primary heart failure are absent, which facilitates differential diagnosis.

Q: Which mediators play a leading role in initiating lung injury?

Cytokines and other biologically active substances with pro-inflammatory action play a leading role in executing the pathological process.

For medical students2 min readUpdated 2026-10-10

Acute Respiratory Distress Syndrome (ARDS) is a prototypical form of external respiration pathology in adults, manifested by acute hypoxemic respiratory failure. The condition is accompanied by bilateral pulmonary infiltration by blood cells, edema, and severe hypoxemia.

MortalityReaches up to 40% in severe cases of the pathology.

Type of EdemaNon-cardiogenic pulmonary edema without signs of primary heart failure.

MediatorsCytokines and pro-inflammatory biologically active substances play a key role in pathogenesis.

StagesExudation, proliferation, and pulmonary fibrosis.

Clinical and Morphological Features

The pathology is characterized by severe damage to the respiratory system. Key manifestations include pronounced hypoxemia, fluid accumulation in lung tissue, and infiltration of the parenchyma by blood cells with a predominance of leukocytes. In the initial stage of the syndrome, clinical signs of primary heart failure are absent, which distinguishes it from cardiogenic edema.

In medical literature and practice, this condition has several synonyms: non-cardiogenic pulmonary edema, "wet lung", "shock lung", "heavy lung", or "moist lung". The name emphasizes the similarity of functional, clinical, and morphological changes with infant respiratory distress syndrome, although their initial pathogenesis and manifestations may differ significantly.

Causes and Etiology

Factors leading to the development of the pathology are divided into infectious and non-infectious. Lung tissue damage can develop directly or indirectly through inflammatory mechanisms.

The following groups of causative factors are distinguished:

Infectious and inflammatory: sepsis, diffuse lung infections, and autoimmune diseases.
Traumatic and iatrogenic: severe shock states, as well as post-operative states following heart-lung transplantation.
Aspiration and toxic: inhalation of toxic gases or fluid aspiration.
Hemodynamic and metabolic: pulmonary edema.

Indirect Lung Injury

A special group consists of primarily extrapulmonary forms of pathology, in which indirect alteration of lung tissue is observed. In this case, lung injury acts as a direct result of the body's systemic inflammatory response.

Such conditions occur against the background of:

Severe soft tissue and internal organ trauma.
Post-transplantation states of the heart-lung complex.
Performance of intra-aortic balloon counterpulsation or cardiopulmonary bypass.
Shock states of various origins.

Stages of Syndrome Development

The pathological process is based on diffuse lung tissue damage. The initiating link of pathogenesis is the activation of the synthesis of biologically active substances with pronounced pro-inflammatory action, among which cytokines play a leading role.

Three sequential stages are distinguished in the development of the process:

Exudative stage.
Proliferative stage.
Pulmonary fibrosis stage.

Mnemonic

E-P-F: Exudation, Proliferation, Fibrosis — the three sequential stages of lung injury in distress syndrome.

Frequently asked questions

Which specific pro-inflammatory cytokines play a leading role in initiating lung injury in ARDS?

Literature indicates that the initiating link is the activation of pro-inflammatory biologically active substances, with cytokines playing a leading role among mediators. Specific mediators associated with ARDS (such as in COVID-19-associated ARDS) include: IL-1, IL-2, IL-6, IL-7, IL-8, IL-9, IL-10, IL-12, IL-17, IL-18, G-CSF, GM-CSF, TNF-alpha, IP-10, IFN-alpha, IFN-beta, MCP-1, and MIP-1alpha.

What morphological and cellular changes occur in the lungs during the proliferation stage?

In the subacute proliferative phase of ARDS, edema and swelling of capillaries and pulmonary parenchyma gradually decrease. Proliferation of type II alveolar epithelial cells and fibroblasts occurs; fibroblasts migrate into the alveolar exudate. Reparative processes take place.

Which oxygenation index (ratio) is used to assess the severity of hypoxemia in ARDS?

The oxygenation index is the PaO2/FiO2 ratio. In respiratory support algorithms for severe community-acquired pneumonia with hypoxemic respiratory failure, therapy escalation depends on this index and clinical severity:

PaO2/FiO2 200–300: standard oxygen therapy; high-flow nasal cannula 30–60 L/min; with COPD or CHF comorbidities — non-invasive ventilation (NIV) with CPAP/EPAP 5–10 cmH2O.
PaO2/FiO2 <150–200: transition to mechanical ventilation; tidal volume 4–8 mL/kg ideal body weight; PEEP 5–8–10 cmH2O (higher if ARDS develops).
PaO2/FiO2 <100–150: mild to deep sedation; neuromuscular blockade.
PaO2/FiO2 <50–80: consider ECMO.

What are the main synonyms for acute respiratory distress syndrome in adults?