Vital Parameters to Monitor in Asthma Patients

Core Vital Parameters for Routine Monitoring

• The American Thoracic Society recommends that peak expiratory flow (PEF) is the single most important objective measure for asthma monitoring and should be measured regularly in all asthmatic patients 1, 2
• Normal PEF values vary by age, sex, and height; patients should know their personal best value, with daily variability >10% in adults or >13% in children being diagnostic of asthma 1, 3
• PEF <50% of predicted or personal best indicates severe asthma requiring immediate treatment, and PEF <33% of predicted or personal best is a life-threatening feature 1, 2
• Respiratory rate >25 breaths/min in adults indicates severe asthma 1, 2
• Heart rate >110 beats/min in adults indicates severe asthma 1, 2

Critical Parameters in Acute Severe Asthma

• Arterial blood gases must always be measured in patients with acute severe asthma admitted to hospital, with a normal or elevated PaCO2 in a breathless asthmatic patient being a marker of life-threatening attack 1, 2
• Severe hypoxia: PaO2 <8 kPa (60 mmHg) despite oxygen therapy is life-threatening 1, 2
• A low pH or high H+ indicates severe respiratory acidosis 1, 2

Spirometry for Severity Classification

• Spirometry provides more reliable and reproducible data than PEF alone, with FEV1/FVC ratio should be >70-80% in healthy adults and >90% in healthy children 3
• FEV1 <70-80% of predicted with reversibility >12% (and >200ml in adults) after bronchodilator confirms asthma 3

Monitoring Frequency

• Home monitoring: PEF should be measured twice daily at consistent times 3
• During acute exacerbations: Reassess PEF 15-30 minutes after bronchodilator treatment 1, 2
• All patients require follow-up within one week of an acute exacerbation 4

Management of Blood Pressure in Asthmatic Patients

Introduction to Beta-Blocker Use

• The American Thoracic Society recommends that beta-blockers can mask tachycardia, one of the key warning signs of severe asthma exacerbation 5

Monitoring and Assessment

• A normal or elevated PaCO2 in a breathless asthmatic is a marker of life-threatening attack and may indicate impending respiratory failure 6, 7
• The severity of asthma attacks is often underestimated due to failure to make objective measurements like peak flow 5, 8

Key Considerations

• Never assume normal oxygen saturation excludes severe asthma exacerbation in a patient on beta-blockers—this combination is particularly dangerous 7