What is Residual volume?

Residual volume (RV) refers to the amount of air that remains in the lungs after a maximum exhalation. In other words, it's the volume of air that cannot be expelled from the lungs, even when a person exhales as forcefully as possible. This residual volume is necessary to keep the lungs inflated and to prevent them from collapsing.

The respiratory system is designed in such a way that there's always a certain amount of air left in the lungs to maintain their structural integrity and allow for gas exchange. The residual volume contributes to maintaining a functional lung structure and ensuring that there's always some air available for gas exchange even after the most forceful exhalation.

Residual volume cannot be measured directly using simple spirometry, which is a common lung function test that measures various parameters of lung function such as tidal volume, inspiratory reserve volume, expiratory reserve volume, and vital capacity. Instead, specialized techniques like body plethysmography or nitrogen washout are used to estimate residual volume accurately.

It's important to note that residual volume, along with other lung volumes and capacities, plays a crucial role in assessing lung health and diagnosing various respiratory conditions such as chronic obstructive pulmonary disease (COPD), asthma, and restrictive lung diseases.