Acute severe asthma

Acute severe asthma
The severity of an attack is easily underestimated.
An atmosphere of calm helps.

Presentation
Acute breathlessness and wheeze.

History
Ask about usual and recent treatment; previous acute episodes and their severity and best peak expiratory flow rate (PEF). Have they been admitted to ITU?

Differential diagnosis
Acute infective exacerbation of COPD, pulmonary oedema, upper respiratory tract obstruction, pulmonary embolus, anaphylaxis.

Investigations
PEF—but may be too ill; arterial blood gases; CXR (to exclude pneumothorax, infection); FBC; U&E.

Assessing the severity of an acute asthmatic attack

Severe attack:
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Respiratory rate >25/min
Pulse rate >110 beats/min
Peak expiratory flow <50% of predicted or best

Life-threatening attack:
Peak expiratory flow <33% of predicted or best
Silent chest, cyanosis, feeble respiratory effort
Bradycardia or hypotension
Exhaustion, confusion, or coma
Arterial blood gases: normal/high PaCO2 >5kPa (36mmHg) PaO2 <8kPa (60mmHg) low pH, eg <7.35