Functional dead space

...However, the parts of the respiratory system that are the pathways through which air passes to the alveoli, i.e. the oral cavity, nasal cavity, pharyngeal cavity, trachea, bronchi, etc., are not involved in gas exchange, so the spatial volume of these parts (about 150 ml) is called dead space or anatomical dead space. However, if some alveoli are not functionally involved in gas exchange due to various reasons, this is also considered a type of dead space, and this dead space, added to the anatomical dead space, is called functional dead space (or physiological dead space). In healthy people, these two dead spaces are almost equal, but in pathological conditions, functional dead space is larger than anatomical dead space. ...

*Some of the terminology that refers to "functional dead space" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…しかし呼吸系のうち肺胞までの空気の通過経路となる部分，すなわち口腔，鼻腔，咽喉頭腔，気管，気管支などはガス交換に関与しないので，これらの諸部分の空間容積(約150ml)を死腔または解剖学的死腔という。ところが種々の原因で一部の肺胞が機能的にガス交換に関与しないような場合，これも一種の死腔と考えられるので，この死腔を前記の解剖学的死腔に加えたものを機能的死腔(または生理学的死腔)といっている。健康人ではこの二つの死腔はほぼ等しいが，病的状態では機能的死腔が解剖学的死腔よりも大きくなる。…

※「機能的死腔」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報