Acute asthma exacerbation in adults

Life-threatening asthma is any one of the following in a patient with severe asthma:[13]British Thoracic Society; Scottish Intercollegiate Guidelines Network. British guideline on the management of asthma. Nov 2024 [internet publication]. https://www.sign.ac.uk/sign-158-british-guideline-on-the-management-of-asthma  

• Silent chest

• Cyanosis

• Poor respiratory effort

• Arrhythmia

• Hypotension

• Exhaustion

• Altered consciousness

• Peak expiratory flow (PEF) <33% of best or predicted

• Oxygen saturation (SpO₂) <92%

• Partial pressure of oxygen (PaO₂) <8 kPa (<60 mmHg) 

• ‘Normal’ partial pressure of carbon dioxide (PaCO₂) 4.6 to 6.0 kPa (35-45 mmHg) 

  • Raised PaCO₂ is a marker of near-fatal asthma.

Acute severe asthma is a patient presenting with any one of the following (and no features of life-threatening asthma):[13]British Thoracic Society; Scottish Intercollegiate Guidelines Network. British guideline on the management of asthma. Nov 2024 [internet publication]. https://www.sign.ac.uk/sign-158-british-guideline-on-the-management-of-asthma

• Patient can’t complete a sentence without taking a breath

• Respiratory rate >25/minute

• Pulse rate > 110 beats per minute

• PEF 33% to 50% of best (use % predicted if recent best unknown).

Indications for moderate asthma are (with no features of life-threatening asthma):[13]British Thoracic Society; Scottish Intercollegiate Guidelines Network. British guideline on the management of asthma. Nov 2024 [internet publication]. https://www.sign.ac.uk/sign-158-british-guideline-on-the-management-of-asthma

• Speech normal

• Respiratory rate <25 breaths/minute

• Pulse rate <110 beats per minute

• PEF >50% to 75% of best or predicted.