CPFT Practice Exam 2026 – Complete Test Prep Guide

The minimum increase needed between pre- and post-bronchodilator testing to identify reversible obstruction is established at 12% or 200 mL. This criterion is based on clinical guidelines that suggest that a significant improvement in lung function, represented by an increase in FEV1 (Forced Expiratory Volume in one second), can indicate the presence of reversible obstructive airway disease, such as asthma.

The 12% change reflects a relevant clinical threshold that helps differentiate between fixed obstructive patterns and those that may respond favorably to bronchodilator therapy. A 200 mL increase also accounts for variations in lung volumes based on the patient's baseline measurements. These values are particularly important in assessing the efficacy of bronchodilators and determining the appropriate management for patients with obstructive lung diseases.

The other options, while they may represent increases that can indicate some degree of improvement, do not align with the established clinical standards specifically for defining reversible obstruction. The correct thresholds are based on consensus from respiratory societies and evidence gathered from clinical practice, making them essential for accurate interpretation of pulmonary function tests.