A FIVC is Forced inspiratory vital capacity.

Forced inspiratory vital capacity (FIVC) is a measure of the maximum amount of air that a person can inhale in a single breath. It is typically measured using a device called a spirometer, which is a device that measures the volume of air that a person inhales and exhales.

To measure FIVC, a person takes a deep breath and then exhales as much air as possible into the spirometer. The spirometer then measures the volume of air exhaled, which represents the person's FIVC. This measurement is used to assess a person's lung function and can be used to diagnose respiratory conditions such as asthma or chronic obstructive pulmonary disease (COPD).