A11. ARDS, definition and basic ventilatory management

From greek.doctor

Acute respiratory distress syndrome (ARDS) is a life-threatening inflammation with oedema in the lungs which leads to severe respiratory failure. It occurs in approx. 10% of ICU patients, and there is a 50% mortality rate.

Etiology

Clinical features

  • Dyspnoea, restlessness, anxiety
  • Altered mental status
  • Cyanosis

Diagnosis and evaluation

Diagnosis by the Berlin criteria. All four must be met:

  1. Respiratory failure within one week of a known cause of ARDS
  2. Bilateral opacities on x-ray or CT
  3. Hypoxaemia (decreased PaO2/FiO2)
    1. The degree of hypoxaemia determines whether it’s mild, moderate, or severe ARDS
  4. Heart failure or fluid overload does not account for the respiratory failure

Management

  • Treat the underlying condition
  • Supportive oxygen therapy (non-invasive ventilation)
    • Non-invasive ventilation may be tried in mild-moderate ARDS, but 50% of patients require intubation later anyway
    • Intubation and invasive ventilation should not be delayed
  • Lung-protective mechanical ventilation (invasive ventilation)
    • Lung-protective ventilation refers to changing the settings of the ventilator to protect the lung from barotrauma and volutrauma during invasive ventilation
    • This means low tidal volume, low plateau pressure, and high positive end-expiratory pressure (PEEP)
    • These settings cause hypercapnia but that’s not a problem and we allow it. This is called permissive hypercapnia
  • Neuromuscular blockers if severe
    • Cisatracurium
    • Must be used early
  • Prone positioning if moderate or severe
  • Fluid overload should be avoided
  • ECMO – if all other methods of oxygenation fail
  • If due to COVID-19: Dexamethasone and tocilizumab