Table 2.

Levels of severity of acute asthma attacks in adults6

Moderate acute asthmaIncreasing symptoms
  • PEFR >50–75% best or predicted

  • No features of acute severe asthma

Severe acute asthmaAny one of the following:
  • PEFR 33%–50% best or predicted

  • Respiratory rate ≥25 breaths/min

  • Heart rate ≥110 beats/min

  • Inability to complete sentences in one breath

Life-threatening asthmaAny one of the following in a patient with severe asthma:
Clinical signs
  • Altered conscious level

  • Exhaustion

  • Arrhythmia

  • Hypotension

  • Cyanosis

  • Silent chest

  • Poor respiratory effort


Measurements
  • PEFR <33% best or predicted

  • SpO2 <92% on air

  • PaO2 <8 kPa on air

  • ‘Normal’ PaCO2 (4.6–6.0 kPa)

Near-fatal asthmaRaised PaCO2 and/or requiring mechanical ventilation with raised inflation pressures
  • PaCO2 = partial arterial pressure of carbon dioxide; PaO2 = partial arterial pressure of oxygen; PEFR = peak expiratory flow rate; SpO2 = oxygen saturation measured by a pulse oximeter.