From the Guidelines
The amount of air forced out of the lungs with maximal forceful expiration is called the forced vital capacity (FVC), which typically ranges from 3-5 liters in healthy adults. This measurement represents the total volume of air that can be exhaled after taking the deepest possible breath. The exact value varies based on several factors including age, sex, height, weight, and ethnicity. FVC is an important pulmonary function test parameter used to assess lung function and diagnose respiratory conditions. During this maneuver, a person inhales as deeply as possible and then exhales as forcefully and completely as possible into a spirometer that measures the volume. The rate at which this air is expelled, particularly in the first second (FEV1), is also clinically significant. Reduced FVC values may indicate restrictive lung diseases like pulmonary fibrosis, while the ratio of FEV1 to FVC helps diagnose obstructive conditions like asthma or COPD. Regular assessment of these values helps monitor disease progression and treatment effectiveness in respiratory conditions. According to the most recent study 1, the use of FVC in relation to FEV1 is recommended for diagnosing airflow obstruction, although the use of slow vital capacity (SVC) may be more sensitive in certain cases.
Some key points to consider when interpreting FVC and FEV1 values include:
- The FEV1/FVC ratio is used to diagnose obstructive lung diseases, with a ratio of less than 0.7 indicating airflow obstruction 1.
- The FVC value can be influenced by factors such as age, sex, and body size, and should be interpreted in relation to predicted values 1.
- The use of FEV1/FEV6 ratio has been suggested as an alternative to FEV1/FVC, but its sensitivity and specificity are not significantly different 1.
- Regular assessment of FVC and FEV1 values is important for monitoring disease progression and treatment effectiveness in respiratory conditions.
Overall, FVC is a crucial parameter in assessing lung function and diagnosing respiratory conditions, and its interpretation should be based on the most recent and highest-quality evidence available 1.
From the Research
Amount of Air Forced Out of the Lung
The amount of air forced out of the lung with maximal forceful expiration is referred to as the Forced Vital Capacity (FVC) or Vital Capacity (VC).
- FVC is the amount of air that can be exhaled from the lungs after a maximal inhalation 2.
- VC is the maximum amount of air a person can expel from the lungs after a maximum inhalation 3.
Measurement of Vital Capacity
Vital capacity can be measured in different ways, including:
- Forced Vital Capacity (FVC): the amount of air that can be exhaled from the lungs after a maximal inhalation 2.
- Slow Vital Capacity (SVC): the amount of air that can be exhaled from the lungs after a maximal inhalation, but at a slower rate [(3,4)].
- Inspiratory Vital Capacity (IVC): the amount of air that can be inhaled into the lungs after a maximal exhalation 4.
Differences in Vital Capacity Measurements
Studies have shown that FVC, SVC, and IVC can be different in individuals with airways obstruction 4.
- FVC is generally smaller than SVC and IVC in individuals with airways obstruction 4.
- The differences between SVC and IVC are small and clinically not important 4.
Clinical Significance
The measurement of vital capacity is important in the diagnosis and management of respiratory diseases, such as chronic obstructive pulmonary disease (COPD) [(2,3,5)].
- The forced expiratory volume in 1 second (FEV1) to FVC ratio is used to diagnose and assess the severity of COPD [(2,3,5)].
- The use of VC instead of FVC can increase the sensitivity of spirometry in detecting airways obstruction [(3,4)].