A11. ARDS, definition and basic ventilatory management

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

Sepsis (most common)
Pneumonia
Aspiration of gastric content
Shock
Acute pancreatitis
Major trauma

Clinical features

Dyspnoea, restlessness, anxiety
Altered mental status
Cyanosis

Diagnosis and evaluation

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

Respiratory failure within one week of a known cause of ARDS
Bilateral opacities on x-ray or CT
Hypoxaemia (decreased PaO2/FiO2)
1. The degree of hypoxaemia determines whether it’s mild, moderate, or severe ARDS
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