Acute Respiratory Distress Syndrome (ARDS)

Overview

• ARDS is a type of respiratory failure due to fluid leakage into alveolar sacs.
• It causes decreased gas exchange and alveoli collapse.
• Leads to decreased oxygen in blood (hypoxemia) affecting organ function.

Anatomy & Physiology Review

• Alveolar sacs: Functional unit of the lungs for gas exchange.
• Blood from the pulmonary artery brings deoxygenated blood to alveoli for reoxygenation.
• Oxygen diffuses into blood; carbon dioxide is exhaled.
• ARDS causes alveolar sacs to fill with fluid, leading to collapse and impaired oxygenation.

Causes

• Systemic inflammation often causes ARDS, seen in hospitalized patients (e.g., sepsis, severe burns).
• Can be caused by indirect sources (e.g., sepsis, inflammation) or direct lung injury (e.g., pneumonia, aspiration).

Pathophysiology & Phases of ARDS

1. Exudative Phase (24 hours post-injury)
   • Damage to capillary membrane leads to fluid leakage into alveolar sacs (pulmonary edema).
   • Protein-rich fluid increases water retention, decreasing surfactant and causing alveolar collapse (atelectasis).
   • Formation of hyaline membrane reduces lung elasticity, leading to decreased lung compliance.
   • Results in VQ mismatch (ventilation-perfusion mismatch) and refractory hypoxemia.
2. Proliferative Phase (14 days post-injury)
   • Lung tissue repair occurs, but new tissue is dense and fibrous, worsening hypoxemia.
3. Fibrotic Phase (3 weeks post-injury)
   • Potential for fibrosis and non-functional lung spaces, leading to poor prognosis.

Signs & Symptoms

• Early: Subtle, normal or diminished lung sounds.
• Progression: Difficulty breathing, hypoxemia, cyanosis, increased heart rate, mental status changes.
• Refractory hypoxemia: Hallmark sign, unresponsive to high oxygen concentrations.
• Chest X-ray: Bilateral infiltrates, "white-out" appearance.

Nursing Interventions

• Goals: Maintain airway and respiratory function; target PAo2 ≥ 60 mmHg, O2 saturation ≥ 90%.
• Mechanical Ventilation: Often with PEEP (Positive End Expiratory Pressure) to open collapsed alveoli.
• Monitoring: Hemodynamic monitoring, watch for complications (e.g., pneumothorax, subcutaneous emphysema).
• Positioning: Prone positioning to improve oxygenation and reduce lung compression.
• Pharmacological Management: Use of corticosteroids, antibiotics, GI drugs, and cardiac drugs as needed.
• Prevent Complications: Monitor for ventilator-acquired infections, pressure injuries, and ensure nutritional support.

Conclusion

• ARDS is a critical condition requiring intensive care.
• Treatment focuses on supporting respiratory function and addressing underlying causes.
• Early recognition and intervention are key to management and improving outcomes.

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