What is the mortality rate of Acute Respiratory Distress Syndrome (ARDS)?

Mortality Rate of ARDS

The current mortality rate of ARDS is approximately 40%, with severe ARDS carrying an in-hospital mortality of 46-60%. 1, 2

Overall Mortality Statistics

• General ARDS mortality is approximately 40%, representing substantial improvement from historical rates of 60-70% reported in early studies 3, 1, 4
• The 28-day mortality rate specifically is 34.8%, with overall in-hospital mortality at 40.0% 4
• Severe ARDS (PaO₂/FiO₂ ≤100 mmHg) carries the highest mortality at 46-60% 1, 2

Mortality by Severity Classification

The mortality rate varies significantly based on ARDS severity using the Berlin Definition:

• Mild ARDS (PaO₂/FiO₂ 200-300 mmHg): Lower mortality, though specific rates not consistently reported 5
• Moderate ARDS (PaO₂/FiO₂ 100-200 mmHg): Intermediate mortality risk 5
• Severe ARDS (PaO₂/FiO₂ ≤100 mmHg): 46-60% in-hospital mortality 1, 2

Primary Causes of Death

Death in ARDS occurs primarily from multi-organ failure and sepsis rather than isolated respiratory failure. 1

• Multi-organ dysfunction syndrome is the leading cause of death, not progressive respiratory failure alone 3, 1
• The number of organ failures is the single most important prognostic indicator for mortality 1
• Liver failure in association with ARDS carries particularly poor prognosis 1
• Unresolved sepsis accounts for the majority of deaths rather than refractory hypoxemia 3

Key Prognostic Factors Affecting Mortality

Poor Prognostic Indicators:

• Development of pulmonary fibrosis during ARDS course significantly worsens outcomes due to vascular bed obliteration and right ventricular strain 1
• Inability to concentrate protein in edema fluid during the first 12 hours (indicating impaired epithelial barrier integrity) predicts poor outcome 1
• Lack of improvement in oxygenation parameters within the first 48 hours 1
• Age, severity of illness, presence of multi-organ failure, and preexisting comorbid conditions 3

Favorable Prognostic Indicators:

• Intact epithelial barrier function with ability to actively transport fluid out of alveoli 1
• Rapid resolution within 10-14 days with parallel decreases in minute ventilation and dead-space ventilation 1
• Improvement in oxygenation parameters within first 48 hours 1

Historical Context and Trends

• Mortality has declined significantly over time, from 60-70% in early reports to the current 40% 3, 1
• Data from Seattle (1983-1993) showed slowly declining mortality rates, particularly in young patients with sepsis-related lung injury 3
• The Lung Injury Score (LIS) provides prognostic stratification: LIS >3.5 correlates with 18% survival, 2.5-3.5 with 30% survival, 1.1-2.4 with 59% survival, and <1.1 with 66% survival 3

Critical Clinical Pitfalls

Do not attribute death solely to respiratory failure—aggressively investigate and manage evolving organ dysfunction, particularly hepatic and cardiovascular systems, as these are the actual causes of mortality 1. The degree of initial hypoxemia is not a reliable prognostic indicator, though changes over 48 hours are more valuable 3, 1. Injurious mechanical ventilation itself can produce cytokine release and end-organ damage, directly contributing to mortality through high driving pressures (≥18 cmH₂O) 1.