Review Question - QID 218226

This patient who presents with sepsis (febrile, tachycardic, likely source of infection from leg wound) and has respiratory decompensation 1 day later with diffuse alveolar opacities requiring ventilator support most likely has acute respiratory distress syndrome. This disease is caused by inflammation resulting in decreased production of surfactant.

Acute respiratory distress syndrome is defined as an acute process causing diffuse inflammation and damage to the lungs. This can be caused by sepsis, aspiration, acute pancreatitis, trauma, amniotic fluid embolism, or uremia. These causes lead to increased vascular permeability and hyperactivation of inflammatory pathways that damage pneumocytes. Decreased type 2 pneumocyte activity results in decreased surfactant production, low lung compliance, and subsequent atelectasis. Patients with acute respiratory distress syndrome will have progressive hypoxia requiring ventilatory support. Treatment strategies include lung-protective ventilation with relatively low tidal volumes and treatment of the source.

Nguyen and Perlman studied the effects of surfactant on lung alveolar tension under conditions similar to acute respiratory distress syndrome. They found that the administration of surfactant reduces tension and theoretically should mitigate injury to lung tissue. They recommend studying methods of treatment for decreasing pulmonary tension.

Figure/Illustration A is a chest radiograph demonstrating ground-glass opacities (red circles) bilaterally. These opacities represent diffuse alveolar infiltrates secondary to acute respiratory distress syndrome.

Incorrect Answers:
Answer 1: Airway obstruction can cause respiratory distress due to the closure of the upper airways. This may occur in response to allergic reactions, bronchospasm, and foreign body obstruction. Patients with airway obstruction would present acutely with respiratory distress with stridor and hyperinflated. Diffuse lung opacities would generally not be seen.

Answer 3: Drug overdose on depressants such as opioids can result in respiratory distress and hypoxemia secondary to suppression of ventilation; however, these patients would have decreased respiratory rate and contracted pupils. Patients may also have pulmonary edema that can be seen as opacity.

Answer 4: Lung parenchymal infection can cause sepsis and hypoxemia due to pneumonia. This would present with fever, dyspnea, and productive cough; however, these patients would have lobar, wedge like opacification in the lungs. The sudden appearance of bilateral infiltrates in a septic patient is more consistent with sepsis induced acute respiratory distress syndrome.

Answer 5: Medication side effect can result in respiratory distress if there is an allergic reaction to the medication; however, anaphylaxis would be seen as closure of the upper airways rather than diffuse fluid infiltration of the alveoli on radiographs. Patients would present with urticaria, wheezing, chest tightness, vomiting, and anxiety.

Bullet Summary:
Acute respiratory distress syndrome is caused by inflammatory damage to pneumocytes and decreased surfactant production in alveoli.