What are the symptoms of Acute Respiratory Distress Syndrome (ARDS)?

Symptoms of Acute Respiratory Distress Syndrome (ARDS)

ARDS presents with severe dyspnea, unremitting tachypnea, and profound hypoxemia that fails to respond adequately to oxygen supplementation, typically developing within one week of a known clinical insult. 1, 2

Primary Respiratory Symptoms

The hallmark respiratory manifestations include:

• Severe dyspnea and unremitting tachypnea that persists despite oxygen supplementation 1
• Profound hypoxemia with PaO2/FiO2 ratio ≤300 mmHg for acute lung injury, ≤200 mmHg for moderate ARDS, and ≤100 mmHg for severe ARDS 3, 1, 2
• Increased work of breathing manifesting as accessory muscle use, paradoxical breathing patterns, and inability to speak in complete sentences 1
• Rapidly progressive respiratory symptoms with acute onset within one week of a known insult or new/worsening respiratory symptoms 3, 2
• Elevated minute ventilation requirements to maintain CO2 excretion due to increased dead space ventilation and intrapulmonary shunting 1

Radiographic Findings

• Bilateral pulmonary infiltrates on chest X-ray without evidence of fluid overload (normal vascular pedicle width and cardiothoracic ratio) 1, 2
• The infiltrates may appear as bilateral, diffuse, peripheral, interstitial patterns but can also present asymmetrically, patchy, or focally 4
• Bilateral pulmonary opacities that cannot be fully explained by cardiac failure or fluid overload 3, 2

Cardiovascular Manifestations

More than 60% of ARDS patients experience hemodynamic instability, which is critical to recognize as circulatory failure is the main factor associated with mortality 3:

• Persistent hypotension requiring vasopressors to maintain mean arterial pressure ≥65 mmHg despite adequate fluid resuscitation 1
• Elevated serum lactate levels (>2 mmol/L) indicating tissue hypoperfusion and anaerobic metabolism 1
• Right ventricular failure precipitated by increased pulmonary vascular resistance from lung collapse and increased afterload 1
• Approximately 65% of patients require catecholamine infusion 3

Neurologic Symptoms

• Altered mental status ranging from confusion to coma 1
• Decreased level of consciousness not attributable to sedation 1
• Delirium with either agitation or lethargy 1

Temporal Evolution of Symptoms

The clinical presentation evolves through distinct phases that fundamentally alter prognosis 4:

• Exudative phase (1-2 days): Initial development of interstitial swelling, proteinaceous alveolar edema, hemorrhage, and hyaline membrane formation 4
• Fibroproliferative phase: Type II alveolar cells proliferate and fibroblasts deposit collagen, marking a critical prognostic juncture 4
• Fibrotic phase (after 10-14 days): Development of pulmonary fibrosis and vascular obliteration with persistently elevated dead-space ventilation despite improving oxygenation, indicating worse outcomes 1, 4

Critical Clinical Context

The number of failing organ systems is the most important prognostic indicator, with mortality increasing exponentially with each additional organ failure 1:

• 28-33% of patients with sepsis meet ARDS criteria at sepsis onset 4
• Death results primarily from multiorgan failure rather than isolated respiratory failure, with overall mortality approximately 40% 1, 4
• Liver failure in association with ARDS carries particularly poor prognosis and should trigger aggressive supportive measures 1, 4

Important Clinical Pitfalls

• The degree of initial hypoxemia is NOT a reliable prognostic indicator 1
• Standard chest X-rays are poor predictors of oxygenation defect severity, clinical outcome, or fibrosis development 4
• After 7-10 days, persistent high minute ventilation requirements despite improving oxygenation indicates developing fibrosis 1
• Failure to recognize evolving multiorgan dysfunction, particularly hepatic and cardiovascular systems, as these determine survival more than respiratory parameters 1