Question

In type II respiratory failure, there is:

• A. Low PO₂ and low PCO₂.
• B. Low PO₂ and high PCO₂.
• C. Normal PO₂ and high PCO₂.
• D. Low PO₂ and normal PCO₂.

Hint:

Type I failure is an oxygenation problem only; type II adds a ventilation problem, so carbon dioxide also rises.

Answer 1

The Correct Option is B

Respiratory failure is graded by what the arterial blood gas shows, and the two types are separated by whether carbon dioxide is also affected.

1. Low PO2 and low PCO2: a drop in carbon dioxide usually reflects hyperventilation, which the body uses early on to compensate for low oxygen. This does not match type II failure.
2. Low PO2 and high PCO2: this is the classic pattern of type II, or ventilatory, failure. The lungs cannot move enough air, so both oxygen intake and carbon dioxide removal suffer together.
3. Normal PO2 and high PCO2: respiratory failure always includes a fall in PO2 by definition, so a normal PO2 rules this option out.
4. Low PO2 and normal PCO2: this fits type I failure, where only oxygenation is impaired while ventilation, and so carbon dioxide clearance, stays intact.

Since type II failure means the lungs cannot ventilate properly, carbon dioxide builds up alongside the fall in oxygen.

Let's summarize:

• Type I failure: low PO2, normal or low PCO2 (an oxygenation problem).
• Type II failure: low PO2, high PCO2 (a ventilation problem).

So the answer is low PO2 with high PCO2.