Ventilation-perfusion ratio

... Humans are usually in an upright position, so the pulmonary blood flow rate is low at the apex of the lung and high at the lower part of the lung due to the influence of gravity. The ventilation distribution also has the same directional difference, but because the difference between the upper and lower blood flow is greater, the ratio of ventilation to blood flow (ventilation-perfusion ratio) is high at the apex of the lung, resulting in high alveolar oxygen partial pressure and low values ​​for both at the lower part of the lung. It is said that pulmonary tuberculosis is more common in the apex of the lung in humans and in the back of the lung in cows, but some people say that both are areas with a high ventilation-perfusion ratio. ...

*Some of the terminology that refers to "ventilation/perfusion ratio" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…　肺循環血流量は，人間はふつう直立位をとっているので，重力の影響を受けて肺尖で少なく，肺下部では多い。換気分布も同じ方向の差があるが，血流の上下差のほうが大きいため，換気と血流の比(換気血流比)は，肺尖で大きく，その結果肺胞気酸素分圧は高く，肺下部ではいずれの値も小さくなる。肺結核はヒトでは肺尖に多く，ウシでは背部に多いといわれるが，いずれも換気血流比の大きい場所にあたるという人がいる。…

※「換気血流比」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