The volume of air in the lungs at various stages of the respiratory cycle is called lung volumes and lung capacities. According to Plantier et al., there are five standard types of lung volumes, namely, Tidal Volume, Inspiratory Reserve Volume, Expiratory Reserve Volume, Residual Volume, and Vital Capacity. TV refers to the amount of air that can be inhaled or exhaled during a single respiratory cycle. This portrays the operations of the breathing centers, respiratory muscles, and lung and chest wall mechanics. IRV is the volume of air that can be forcedly inhaled after a regular tidal volume has been reached. ERV is the volume of air that can be forcedly breathed in after a standard tidal volume is reached. RV is the amount of air that remains in the lungs after a complete exhalation. The measurement of lung volumes is an essential component of the pulmonary function test.
The limit amount of air a person can exhale from the lungs after maximum breathing is called Vital Capacity (VC). VC is measured by using an instrument known as a spirometer by breathing into a mouthpiece connected to it as the patient is sitting. The spirometer measures the amount and rate at which you breathe in and out over time. One can breathe normally and gently during some of the test measurements. Some tests necessitate a forcible inhalation or exhalation following a deep breath. This information enables one healthcare provider to diagnose and treat diagnosed lung illnesses.