Respiratory volumes are different amounts of air moved during specific breathing activities. Tidal volume (TV) is the volume of air moved during normal breathing. Inspiratory reserve volume (IRV) is the extra air that can be inhaled after a deep breath, while expiratory reserve volume (ERV) is the extra air exhaled forcefully after a normal exhalation. Residual volume (RV) is the air that remains in the lungs after maximal exhalation. Minimal volume (MV) is significant in determining stillbirth or post-birth death.