Assess the severity of the symptoms:

• Mild:
• Occasional barking cough and no audible stridor at rest.
• No or mild suprasternal and/or intercostal recession.
• The child is happy and is prepared to eat, drink, and play.
• Moderate:
• Frequent barking cough and easily audible stridor at rest.
• Suprasternal and sternal wall retraction at rest.
• No or little distress or agitation.
• The child can be placated and is interested in its surroundings.
• Severe:
• Frequent barking cough with prominent inspiratory (and occasionally, expiratory) stridor at rest.
• Marked sternal wall retractions.
• Significant distress and agitation, or lethargy or restlessness (a sign of hypoxaemia).
• Tachycardia occurs with more severe obstructive symptoms and hypoxaemia.
• Impending respiratory failure may develop regardless of the severity of the symptoms:
• The presence of any of these signs overrides any other clinical signs:
• Change in mental state, such as lethargy and listlessness or decreased level of consciousness.
• Pallor.
• Dusky appearance.
• Tachycardia.
• In children with impending respiratory failure, breathing may be laboured, a barking cough may not be prominent, stridor at rest may be hard to hear, and sternal wall retractions may not be marked.
• A child who appears to be deteriorating but whose stridor appears to be improving has worsening airways obstruction and is at high risk of complete airway occlusion.