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

Step 1: Understanding the Question.
Respiratory failure is split into two types based on the arterial blood gas pattern, and the question asks which pattern defines type II.

Step 2: Key Concept.
Type I respiratory failure is a problem of oxygenation alone, so PO2 falls while PCO2 stays normal or even falls. Type II respiratory failure is a problem of ventilation, meaning the lungs cannot clear carbon dioxide, so PCO2 rises along with a fall in PO2.

Step 3: Detailed Explanation.
Option (1) low PO2 and low PCO2: a low PCO2 happens when a patient hyperventilates to compensate for low oxygen, which is closer to early type I failure, not type II.
Option (2) low PO2 and high PCO2: this is the exact definition of type II, or ventilatory, respiratory failure, seen in conditions like COPD, chest wall disease, and neuromuscular weakness where the patient cannot move enough air.
Option (3) normal PO2 and high PCO2: PO2 is always low in respiratory failure by definition, so a normal PO2 does not fit either type.
Option (4) low PO2 and normal PCO2: this describes type I respiratory failure, where gas exchange for oxygen fails but carbon dioxide clearance is preserved.

Step 4: Final Answer.
Type II respiratory failure has both low PO2 and high PCO2.
\[ \boxed{\text{Low PO}_2 \text{ and high PCO}_2} \]