Forced Expiratory Volume in one second (FEV1) represents the volume of air a subject can forcefully expel from their lungs in one second. Determining this value usually involves spirometry, a pulmonary function test performed using a device called a spirometer. The individual takes a maximal inspiration and then exhales as forcefully and completely as possible into the spirometer. The device measures the volume of air expelled over time. The highest volume exhaled within the first second is recorded as the FEV1. For instance, if an individual inhales deeply and then exhales 4.0 liters of air in the first second, their FEV1 is 4.0 liters.
This measurement is a crucial indicator of lung function and airflow obstruction. Clinicians utilize it extensively in the diagnosis and management of respiratory conditions like asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis. Tracking changes in this metric over time can help assess disease progression, monitor treatment effectiveness, and predict future respiratory events. Historically, its inclusion in respiratory evaluations has allowed for standardized assessments and comparisons across different individuals and populations, contributing significantly to advancements in pulmonology.
