What does decreased FEF 25-75 signify?

Decreased FEF 25-75, or Forced Expiratory Flow at 25% to 75% of the forced vital capacity, indicates a reduction in airflow in the mid-range of the expiration. This measurement specifically assesses the function of the small airways of the lungs. When the FEF 25-75 is decreased, it often signifies that there is some form of obstruction in these airways, which can be the result of conditions such as asthma or chronic obstructive pulmonary disease (COPD).

This mid-expiratory flow rate is particularly sensitive to changes in small airway function, making it a useful indicator of small airway obstruction. In contrast, abnormalities in other measurements, such as the forced vital capacity or forced expiratory volume in one second (FEV1), may not capture issues restricted to these smaller airways.

While options like lung hyperinflation, high lung compliance, and normal respiratory function may reflect various pulmonary conditions, they do not specifically align with the implications of a decrease in FEF 25-75, which is firmly linked to small airway obstruction.