Acute Asthma - Assessment

Make an initial assessment of the severity of acute asthma based upon a combination of

• clinical features, 
• peak flow measurement and 
• pulse oximetry 

This is as outlined as below.

Moderate exacerbation of asthma
• Increasing symptoms.
• Peak fl ow 50–75 % best or predicted.
• No features of acute severe asthma (below).

Acute severe asthma
Any one of the following:
• Inability to complete sentences in 1 breath.
• Respiratory rate ≥25/min.
• Heart rate ≥110/min.
• Peak flow 33–50 % best or predicted.


Life-threatening asthma
A patient with severe asthma with any one of the following:
• Cyanosis.
• Exhaustion, confusion, coma.
• Feeble respiratory effort.
• SpO 2 <92 % .
• Silent chest.
• Bradycardia, arrhythmia, hypotension.
• pO 2 <8kPa.
• Normal pCO 2 (4.6–6.0kPa).
• Peak fl ow <33 % best or predicted.

Near fatal asthma
• Increased pCO 2 and/or requiring mechanical ventilation with increased inflation pressures.

Other investigations
- Obtain ABG if SpO 2 <92 % or if there are other features of life-threatening asthma.
- Obtain a CXR (without delaying treatment) if there is:
• Suspected pneumomediastinum or pneumothorax.
• Suspected consolidation.
• Life-threatening asthma.
• Failure to respond to treatment satisfactorily.
• Requirement for ventilation