A comparative study of bronchodilator response: utilizing pre-bronchodilator versus predicted normal values.

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology

Background:

• The standard definition of a positive bronchodilator response involves a 12% increase and 0.2 L absolute change in FEV₁ or FVC from pre-bronchodilator values.
• Recent guidelines suggest using percent changes relative to predicted normal values, but their application in patients with airflow obstruction requires further investigation.

Purpose of the Study:

• To compare the conventional bronchodilator response definition with a method using predicted normal values.
• To evaluate these approaches across a spectrum of pre-bronchodilator FEV₁ and FVC values.

Main Methods:

• A retrospective analysis of 1,040 patients undergoing spirometry and bronchodilator testing was performed.
• Changes in FEV₁ and FVC were calculated both as a percentage of pre-bronchodilator values and as a percentage of predicted normal values.

Main Results:

• Using predicted normal values identified a positive bronchodilator response in 5.7% of patients for FEV₁ and 5.8% for FVC, compared to 19.0% and 12.7% respectively, when using pre-bronchodilator values.
• These discrepancies persisted even when considering the absolute change of ≥0.2 L.
• For unobstructed patients, thresholds for a positive response were 14% for FEV₁ and 10% for FVC relative to predicted normal values.

Conclusions:

• Calculating bronchodilator response relative to predicted normal values significantly reduces the overestimation of response, particularly in individuals with low pre-bronchodilator FEV₁.
• The study proposes new criteria for a positive bronchodilator response: a ≥14% change in FEV₁ and a ≥10% change in FVC relative to predicted normal values.