How is reversibility post Albuterol determined on spirometry?

Determining Reversibility Post-Albuterol on Spirometry

Reversibility on spirometry is defined as an increase in FEV1 of both greater than 200 mL AND 15% increase over the pre-bronchodilator value. 1

Patient Preparation

Before conducting reversibility testing, proper patient preparation is essential:

• Withhold medications prior to testing:
  • Short-acting bronchodilators for 4-6 hours
  • Long-acting β-agonists for 12 hours
  • Sustained-release theophyllines for 24 hours
  • Oral slow-release β-agonists for 12 hours 2, 1
• Patient should avoid smoking for 1 hour prior to and throughout testing
• Ensure patient is clinically stable and free from respiratory infections 1

Testing Protocol

1. Baseline Measurement:

   • Perform three acceptable tests of FEV1, FVC, and PEF
   • Record the best values from these tests 2

2. Albuterol Administration:

   • After a gentle incomplete expiration, administer 100 μg of albuterol via a valved spacer device
   • Patient inhales in one breath to total lung capacity (TLC)
   • Hold breath for 5-10 seconds before exhaling
   • Deliver four separate doses (total 400 μg) at 30-second intervals 2

3. Post-Bronchodilator Measurement:

   • Wait 15-20 minutes after albuterol administration
   • Perform three acceptable spirometry maneuvers
   • Record the best post-bronchodilator values 2, 1

Interpretation Criteria

• Positive Reversibility: An increase in FEV1 that is:

  • ≥200 mL absolute increase AND
  • ≥15% increase from pre-bronchodilator value 1

• Clinical Significance:

  • In asthma: Typically shows significant reversibility (all asthmatics in one study) 3
  • In COPD: May show limited or no reversibility in FEV1 3, 4
  • A negative FEV1 response does not preclude clinical benefit from bronchodilators in terms of improved walking distance and reduced breathlessness 1

Special Considerations

• Low Baseline FEV1: In patients with very low baseline FEV1 (<1 liter), consider adjusting calculations to account for the variability at low values 4

• Normal Baseline Spirometry: Bronchodilator testing can be omitted in patients with normal spirometry and FEV1 >90% of predicted, as they have a low probability (<2%) of a positive response 5

• Dose Considerations: The standard 400 μg dose ensures response is high on the albuterol dose-response curve. A lower dose can be used if there are concerns about cardiac effects or tremor 2

• Combined Testing: For more comprehensive assessment, especially in COPD, consider combination testing with both albuterol and anticholinergics (e.g., ipratropium), which may identify reversibility more effectively than either agent alone 6

Common Pitfalls to Avoid

• Inadequate Medication Withholding: Failure to withhold bronchodilators for the appropriate time can lead to false-negative results

• Improper Technique: Poor inhalation technique may result in inadequate drug delivery and underestimation of reversibility

• Inconsistent Timing: Measuring too early or too late after bronchodilator administration can miss peak bronchodilator effect

• Ignoring Small Changes: In severely obstructed patients, even small absolute changes may represent significant physiological improvement

• Relying Solely on FEV1: Consider changes in other parameters such as FVC, which may show significant improvement even when FEV1 does not, especially in patients with air trapping