From the Guidelines
The Forced Expiratory Flow (FEF) 25-75 is the mean forced expiratory flow between 25% and 75% of the Forced Vital Capacity (FVC).
Definition and Measurement
- The FEF 25-75 is also known as the maximum mid-expiratory flow 1.
- It is measured with an accuracy of at least ±5% of reading or ±0.200 L·s-1, whichever is greater, over a range of up to 7 L·s-1 1.
- The FEF 25-75 is highly dependent on the validity of the FVC measurement and the level of expiratory effort 1.
Clinical Significance
- The FEF 25-75 is used to assess small airways function 1.
- A reduced FEF 25-75 may be related to small airway obstruction, although this is a subject of discussion 1.
- The FEF 25-75 is collected to detect comorbidities such as asthma or COPD (in older patients) and to assess airway function in patients with osteogenesis imperfecta (OI) 1.
Calculation and Prediction Equations
- The FEF 25-75 can be calculated using the formula: FEF 25-75 = 0.3080 exp(0.0165) (height in cm) 1.
- Other prediction equations for FEF 25-75 are available, depending on the population and age range being studied 1.
From the Research
Definition of Forced Expiratory Flow (FEF) 25-75
- The Forced Expiratory Flow (FEF) 25-75, also known as the forced mid-expiratory flow, is a measure of the rate of airflow during a forced exhalation between 25% and 75% of the vital capacity 2, 3, 4, 5, 6.
- It is a potentially sensitive marker of obstructive peripheral airflow and can be used to assess the function of the small airways 2, 3, 4, 5, 6.
Clinical Significance of FEF 25-75
- A low FEF 25-75 value has been associated with an increased risk of developing chronic obstructive pulmonary disease (COPD) 2 and airway hyperresponsiveness 3.
- FEF 25-75 has been shown to be a useful predictor of COPD development in patients with normal lung function 2.
- A lower FEF 25-75 value has also been linked to more severe disease, increased symptoms, and decreased lung function in patients with COPD 4.
- FEF 25-75 may be a valuable tool in identifying early pathology in COPD and asthma, even in the absence of other abnormal spirometry values 5, 6.
Relationship to Airflow Limitation and Disease Severity
- FEF 25-75 has been shown to decrease with increasing airflow limitation severity 5.
- A lower FEF 25-75 value has been associated with increased emphysema, functional small airways disease, and airway wall thickness in patients with COPD 4.
- FEF 25-75 may be a useful marker of disease severity and progression in COPD and asthma 4, 5, 6.