Anatomical Dead Space

Medical definition of anatomical dead space.

Anatomical dead space. Anatomical dead space is that portion of the airways such as the mouth and trachea to the bronchioles which conducts gas to the alveoli. Anatomic dead space is the total volume of the conducting airways from the nose or mouth down to the level of the terminal bronchioles and is about 150 ml on the average in humans. The volume of the conducting airways from the external environment at the nose and mouth down to the level at which inspired gas exchanges oxygen and carbon dioxide with pulmonary capillary blood. In healthy lungs where the alveolar dead space is small fowler s method accurately measures the anatomic dead space by a nitrogen washout technique.

The dead space in that portion of the respiratory system which is external to the alveoli and includes the air conveying ducts from the nostrils to the terminal bronchioles compare physiological dead space. Formerly presumed to extend down to the beginning of alveolar epithelium in the respiratory bronchioles but more recent evidence indicates that effective gas exchange extends some distance up the thicker walled conducting airways because of rapid longitudinal mixing. The anatomic dead space fills with inspired air at the end of each inspiration but this air is exhaled unchanged.