What does forced expiratory volume (FEV1) measure?

• A. The total lung capacity
• B. The volume of air exhaled in one second
• C. The residual volume of the lungs
• D. The tidal volume during quiet breathing

Answer: (B)

Forced expiratory volume in one second, commonly referred to as FEV1, specifically measures the volume of air that can be forcibly exhaled from the lungs in the first second of a breath. This parameter is critical in assessing lung function, particularly in diagnosing and monitoring respiratory conditions such as asthma, chronic obstructive pulmonary disease (COPD), and other obstructive and restrictive lung diseases. A reduced FEV1 often indicates a limitation in airflow, which helps healthcare professionals evaluate the severity of a patient's condition and make informed decisions regarding treatment and management.

The other choices relate to different aspects of lung function. Total lung capacity refers to the maximum amount of air the lungs can hold, while residual volume is the volume of air remaining in the lungs after a forceful exhalation. Tidal volume denotes the amount of air inhaled or exhaled during normal breathing. As such, these measurements serve distinct purposes and do not reflect the specific function that FEV1 assesses.