2.14 Acute Respiratory Distress Syndrome (ARDS)

Pulmonary system review for the USMLE Step 1 Exam

• Acute respiratory distress syndrome (ARDS) is an acute, diffuse, inflammatory form of lung injury that is life-threatening for patients.
• ARDS is a response from the lungs to severe injury, most commonly caused by sepsis, but can also be caused by pneumonia, trauma, drowning, toxin inhalation, and pancreatitis.
• The lung injury from sepsis causes systemic inflammation, damaging lung tissue and causing diffuse alveolar damage, reducing surfactant production and causing alveolar edema.
• Patients with ARDS will present with progressive cough, progressive dyspnea, and hypoxia, and usually deteriorate quickly, 12-24 hours after symptom onset.
• Diagnosis of ARDS is based on imaging findings of bilateral lung infiltrates seen as white-out on chest X-ray and ground glass opacities on CT, as well as a decreased Pao2/Fio2 ratio to less than 300.
• Patients with ARDS are placed on mechanical ventilation with low tidal volume and positive end expiratory pressure (PEEP) to keep the alveoli open at the end of the respiratory cycle.
• Treatment of ARDS involves addressing the underlying cause of the disease, such as sepsis or pneumonia.