Question

When the value of V/q is infinity, it means?

• A. No \(O_2\) goes from alveoli to blood and no \(Co_2\) goes from blood to alveoli
• B. Dead space
• C. The \(PO_2\) of alveolar air is 159 mmHg and \(PCO_2\) is 40 mmHg
• D. Partial pressure of \(O_2\) and \(CO_2\) are equal

Answer 1

The Correct Option is B

To solve the problem of understanding what it means when the value of V/q is infinity, let's break down each term:

• V stands for ventilation, which is the amount of air reaching the alveoli in the lungs.
• Q stands for perfusion, which is the blood flow in the capillaries around the alveoli.
• The V/q ratio is thus the ratio of air reaching the alveoli to the blood that can absorb the air.

An ideal V/q ratio is around 0.8, where ventilation and perfusion are effectively matched for optimal gas exchange. If V/q is at infinity, it implies:

• The denominator (q or perfusion) is approaching zero, indicating negligible or no blood flow to the alveoli.
• With continuous ventilation and absent or greatly reduced blood circulation, this state is termed dead space.

Therefore, the correct answer is Dead space, where adequate ventilation occurs without corresponding perfusion, meaning no effective gas exchange can occur as there’s no blood to transport oxygen and remove carbon dioxide.