Pulmonary Dead Space Ventilation
While a portion of each inspired tidal volume is obligated to the conducting airways, another portion may end up in alveoli that are not perfused with pulmonary capillary blood. In both cases, this air does not participate in gas exchange with the capillary blood. The volume of air occupying the conducting airways or nonperfused alveoli is referred to as the dead space volume (VD). It is possible to calculate dead space ventilation (D) by multiplying the VD by the number of breaths per minute. Two different but closely related types of pulmonary dead space are recognized, the anatomic and physiologic dead space.