Moderate, acute severe, life threatening and near fatal
Expansion
| Grade | Features |
|---|---|
| Moderate | Peak flow 50 to 75 per cent, no features of severe asthma |
| Acute severe | Peak flow 33 to 50 per cent, respiratory rate 25 or more, heart rate 110 or more, unable to complete sentences |
| Life threatening | Peak flow under 33 per cent, saturations under 92 per cent, and the features below |
| Near fatal | Raised carbon dioxide, or requiring ventilation |
Life threatening features, using CHEST:
- C - Cyanosis and Confusion
- H - Hypotension
- E - Exhaustion
- S - Silent chest
- T - Tachyarrhythmia or bradycardia
Plus a peak flow under 33 per cent, saturations under 92 per cent, and a normal carbon dioxide.
Why a normal carbon dioxide is alarming: in acute asthma the patient hyperventilates, so the carbon dioxide should be low. A normal value means ventilation is failing to keep pace, and a raised value means it has already failed. This is the single most misread number in acute asthma.
Similarly a silent chest means airflow is too low to generate wheeze, so the disappearance of wheeze in a deteriorating patient is not improvement.
Risk factors for a fatal attack: previous near fatal asthma or intensive care admission, three or more classes of asthma medication, heavy short acting beta agonist use, repeated attendances, poor adherence, brittle asthma, and adverse psychosocial circumstances.
A patient with life threatening features needs immediate senior and critical care involvement, and should never be left unattended.