Assessment

Factors to consider include:

• pulse rate: (1)
  • if the tachycardia is persistently 120 to 140 beats per minute the patient is still in danger
  • a falling pulse rate is an ominous feature
    
    
• appearance of patient: (2)
  • character of breathing
  • facial expression
  • position in bed
    
    
• peak flow rate: (2)
  • is an objective measurement of progress
  • it can be measured before and after nebulisers
    
    
• estimation of blood gas tensions:
  • it is necessary to monitor the PaO2 and PaCO2
  • a rise in the PaCO2 suggests respiratory failure and intermittent positive pressure ventilation should be considered

Life-threatening asthma is any one of the following in a patient with severe asthma: (2)

• Silent chest
• Cyanosis
• Poor respiratory effort
• Arrhythmia
• Hypotension
• Exhaustion
• Altered consciousness
• PEF <33% of best or predicted
• SpO2 <92%
• PaO2 <8 kPa (<60 mmHg)
• ‘Normal’ PaCO2 (4.6-6.0 kPa [35-45 mmHg]) - raised PaCO2 is a marker of near-fatal asthma.

Acute severe asthma is a patient presenting with any one of the following (and no features of life-threatening asthma): (2)

Patient can’t complete a sentence without taking a breath

Respiratory rate ≥25/minute

Pulse rate ≥ 110 beats per minute

PEF 33% to 50% of best (use % predicted if recent best unknown).

Indications for moderate asthma are: (2)

Speech normal

Respiratory rate <25 breaths/minute

Pulse rate <110 beats per minute

PEF 50% to 75% of best or predicted.

References

1. Global Initiative for Asthma (GINA). Global strategy for asthma management and prevention. 2023 [internet publication].
2. British Thoracic Society; Scottish Intercollegiate Guidelines Network. British guideline on the management of asthma: a national clinical guideline. Jul 2019 [internet publication]