Which of the following would you expect to occur if ventilation to an area of the lung remained constant but perfusion to this same area decreased?
I .The PACO₂ should fall.
II.The PAO₂ should fall.
III.The $\dot { V }$ / $\dot { Q }$ ratio should rise.

Question

Which of the following would you expect to occur if ventilation to an area of the lung remained constant but perfusion to this same area decreased?
I .The PACO₂ should fall.
II.The PAO₂ should fall.
III.The

\dot { V }

/

\dot { Q }

ratio should rise.

Quizplus · Accepted Answer

If perfusion decreases but ventilation remains constant, the alveolar partial pressure of oxygen (PAO2) should fall (as oxygen is not being delivered to the alveoli), but the alveolar partial pressure of carbon dioxide (PACO2) should remain constant (as carbon dioxide can still diffuse out of the alveoli). This results in a rise in the PAO2/PACO2 ratio. Therefore, only III is true. Additionally, since there is less oxygen in this area of the lung, the oxygen content of the blood leaving this area should also be decreased (I).

Which of the Following Would You Expect to Occur If V˙\dot { V }V˙

Which of the Following Would You Expect to Occur If $\dot { V }$