What are the guidelines for Pulmonary Function Tests (PFTs) and initial treatment for conditions like asthma and Chronic Obstructive Pulmonary Disease (COPD)?

Guidelines for Pulmonary Function Tests (PFTs) and Initial Treatment for Asthma and COPD

Pulmonary function testing is essential for the diagnosis and management of both asthma and COPD, with spirometry being the gold standard test that must be performed on all patients with suspected respiratory disease to confirm diagnosis and guide treatment decisions. 1, 2

Pulmonary Function Testing Guidelines

Spirometry Requirements

• FEV1 measurement is the preferred choice for COPD diagnosis and monitoring because:
  • It provides reproducible, objective measurements with well-defined normal ranges
  • Can be measured at all disease stages
  • Has low variance between repeated measurements (changes >200ml are clinically significant)
  • Predicts mortality and correlates with breathlessness severity
  • Enables disease progression monitoring 1

Diagnostic Criteria

• For Asthma:

  • Compatible clinical history plus objective confirmation of variable expiratory airflow limitation
  • Diagnostic criteria includes at least one of:
    1. Positive bronchodilator response (FEV1 increase >12% and >200ml in adults)
    2. Excessive variability in twice-daily PEF over 2 weeks
    3. Lung function improvement after 4 weeks of ICS treatment
    4. Positive bronchial challenge test
    5. Excessive variation in lung function between visits 1

• For COPD:

  • Post-bronchodilator FEV1/FVC ratio <70%
  • FEV1 <80% predicted with little variability in serial PEF measurements
  • Normal FEV1 effectively excludes COPD diagnosis 1, 2

Severity Classification

• COPD Severity Classification:
  • Mild: FEV1 60-80% predicted
  • Moderate: FEV1 40-59% predicted
  • Severe: FEV1 <40% predicted 1, 2

Bronchodilator Reversibility Testing

• Must be performed when patients are clinically stable and free from infection
• Patients should withhold:
  • Short-acting bronchodilators for 6 hours
  • Long-acting β-agonists for 12 hours
  • Sustained-release theophyllines for 24 hours
• Recommended protocol:
  • Measure before and 15 minutes after 2.5-5mg nebulized salbutamol/5-10mg terbutaline, OR
  • Before and 30 minutes after 500μg nebulized ipratropium bromide, OR
  • Before and 30 minutes after both in combination 1

Corticosteroid Reversibility Testing

• Measure spirometry before and after:
  • Oral prednisolone 30mg daily for 2 weeks, OR
  • Inhaled corticosteroid (e.g., beclomethasone) for 6 weeks 1

Initial Treatment Guidelines

Asthma Treatment

1. Mild Disease:

   • Short-acting β2-agonists as needed based on symptomatic response 1

2. Moderate Disease:

   • Regular inhaled corticosteroids (ICS)
   • Short-acting bronchodilators as needed
   • Consider long-acting bronchodilators if symptoms persist 1

3. Severe Disease:

   • Higher-dose ICS plus long-acting β2-agonists
   • Consider referral to asthma specialists for assessment of eligibility for biologic therapies 1

COPD Treatment

1. Mild Disease (FEV1 60-80% predicted):

   • Short-acting bronchodilator (β2-agonist or anticholinergic) as needed based on symptomatic response 1, 2

2. Moderate Disease (FEV1 40-59% predicted):

   • Regular therapy with short-acting bronchodilators or combination therapy
   • Consider corticosteroid trial in all patients 1, 2

3. Severe Disease (FEV1 <40% predicted):

   • Combination therapy with regular β2-agonist and anticholinergic
   • Consider corticosteroid trial
   • Assess for home nebulizer use
   • Consider long-term oxygen therapy if PaO₂ <7.3 kPa 1, 2

Implementation Considerations

Spirometry Access Options

1. Open access to hospital lung function laboratories for primary care
2. Individual practice-based spirometry (requires proper training and quality control)
3. Mobile community spirometry service 1

Common Pitfalls to Avoid

• Misdiagnosis: Relying solely on symptoms without objective PFT confirmation
• Inadequate Testing: Abbreviated expiratory maneuvers can underestimate FVC in COPD
• Improper Technique: Spirometry requires trained staff to perform tests to published standards
• Misinterpretation: Electronic spirometers without hard copy tracings may lead to underestimation of FEV1 and FVC 1
• Overreliance on PEF: PEF may underestimate the degree of airway obstruction in COPD 1

Quality Control Requirements

• Volumetric devices need weekly calibration
• Flow-based devices need daily calibration with a three-liter syringe
• Spirometers should produce hard copies of tests with volume/time plots
• At least three technically satisfactory readings are required
• At least two FEV1 readings should be within 100ml or 5% of each other 1

By following these guidelines, clinicians can accurately diagnose respiratory conditions and initiate appropriate treatment to reduce morbidity, mortality, and improve quality of life for patients with asthma and COPD.