Table 1 Method of determining the severity of an asthma episode.

Severity*	Accessory muscle use	Wheeze	Dyspnoea	Oxygen saturation (%) on room air	Peak expiratory flow rate (% of predicted)
Mild	None or minimal intercostal retractions	Normal breathing or end‐expiratory wheezing	Normal activity and speech or minimal dyspnoea	>95	>70
Moderate	Intercostal and substernal retractions	Pan‐expiratory wheezing	Decreased activity or speaking 5–8‐word sentences	91–95	51–70
Severe	Nasal flaring or suprasternal retraction	Wheeze audible without stethoscope	Decreased activity or speaking <5‐word sentences	86–90	41–50
Critical	Nasal flaring or paradoxical chest movement	Silent chest or wheeze audible without stethoscope	Unable to speak 1–2‐word sentences or no vocalisations	<86	⩽40

*An acute episode was rated at a given level of severity if the patient had ⩾2 clinical signs for that level and ⩽1 feature in any other level.