The total volume of the respiratory tract that is not functionally involved in gaseous exchange. It is estimated by combining the anatomical dead space with a figure derived from the volume of alveoli, which are well-ventilated, but poorly perfused with blood so that they are less efficient at exchanging gas with the blood. In healthy individuals, physiological dead space is roughly equivalent to anatomical dead space because all areas of the lungs are usually well-perfused with blood. However, in patients with lung malfunctions or disease, physiological dead space may be much greater than anatomic dead space. See also alveolar dead space, lung volumes.
Subjects: Sports and Exercise Medicine.