Assessment Of Asthma Exacerbations In Adults

BTS Guidelines

Moderate asthma exacerbation

• Increasing symptoms
• PEF > 50-75% predicted
• No features of acute severe asthma

Acute severe asthma
Any one of:

• PEF 33-50% best or predicted
• Respiratory rate ≥ 25/min
• Tachycardia (≥ 110 bpm)
• Inability to complete sentences in one breath

Life-threatening asthma
Any one of:

• PEF < 30%
• SpO₂ < 92%; PaO₂ < 8 kPa
• Normal PaCO₂ (4.6-6 kPa)
• Silent chest
• Cyanosis
• Poor respiratory effort (i.e. giving up)
• Arrhythmia (e.g. tachycardia)
• Exhaustion, altered consciousness level

Near fatal asthma
Raised PaCO₂ and/or requiring mechanical ventilation with raised inflation pressure.