This is comprised of two segments: the anatomic dead space (parts of the airway that are not alveolar exchange membranes) and the alveolar dead space (alveoli that are ventilated but not perfused with pulmonary capillary blood flow).

Structure and Functionĭead space of the respiratory system refers to the volume of inspired air in a given breath in which oxygen (O2) and carbon dioxide (CO2) gasses are not exchanged across the alveolar membrane in the respiratory tract. However, differences in the exact way of measuring this space result in clinically significant different results and, therefore, debate remains about the true value of this measured parameter. Indeed, it may serve as a prognostic factor in patients with acute repository distress syndrome (ARDS) who require ventilation.

This phenomenon has clinical significance because, both in healthy and impaired lungs, properly calculating and accounting for this non-physiological space is important for the proper respiratory care of ventilated patients. This is therefore termed anatomical dead space as it serves no respiratory function. Anatomic dead space is an important phenomenon in respiratory physiology whereby, owing to the fact that upper airways do not function as locations for gas exchange, and because of the tidal nature of ventilation, there is always a fraction of the inspired air that does not perform a physiologic function of exchanging carbon dioxide for oxygen.

Dead space physiology