The vital capacity is called the sum total volume of air that can be expired after maximum inhalation or maximum air that a person can breathe in after forced expiration. It is very important to measure a person’s respiratory health.
A decreased vital capacity also seems to be an indication of restrictive lung disease where the lungs cannot expand out completely.
In such cases of normal vital capacity, this improper functioning of the lungs indicates obstructive lung disease where the lungs are blocked in the airways.