What is static lung volume?

Static lung volumes are those measured when there is no airflow into or out of the lungs, typically during a breath hold.

When the respiratory muscles are neither contracting nor relaxing, the lungs recoil and the chest cavity expands until the elastic recoil pressure of the lungs equals the elastic recoil pressure of the chest wall. These two opposing elastic pressures are equal at a point called functional residual capacity (FRC).

The three static lung volumes are:

- Tidal volume (VT): The volume of air moved in and out with each breath.

- Inspiratory reserve volume (IRV): The volume of air that can be inspired above the tidal volume.

- Expiratory reserve volume (ERV): The volume of air that can be expired below the tidal volume.