Investigations

First line investigation:

• PEFR
• blood gases:
  • hypoxia is common usually requiring the administration of oxygen
  • hypercapnia may suggest respiratory failure and artificial ventilation should be considered

Other investigation:

• full blood count
• blood cultures
• urea and electrolytes to check for dehydration
• chest radiography to check for pneumothorax

If the patient has any features indicating a life-threatening asthma exacerbation, measure arterial blood gas. No other investigations are immediately required prior to starting management (1)

Reference

1. British Thoracic Society; Scottish Intercollegiate Guidelines Network. British guideline on the management of asthma: a national clinical guideline. Jul 2019 [internet publication].