20/07/2026
✅ Correct Answer: A. pH 7.29, PCO₂ 56, PaO₂ 83, HCO₃ 22
Rationale
In acute respiratory failure, the client has impaired gas exchange. This commonly leads to CO₂ retention and respiratory acidosis.
Expected ABG findings include:
Low pH → acidosis
High PaCO₂ → respiratory cause
Low or decreased PaO₂ → impaired oxygenation
Normal or slightly changed HCO₃⁻ → little compensation in acute cases
Option A shows respiratory acidosis with elevated CO₂ and low pH, which is consistent with acute respiratory failure.
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Option Analysis
✅ A. pH 7.29, PCO₂ 56, PaO₂ 83, HCO₃ 22
Correct. Low pH and elevated PCO₂ indicate respiratory acidosis, commonly seen in acute respiratory failure.
❌ B. pH 7.38, PCO₂ 40, PaO₂ 92, HCO₃ 25
Incorrect. These values are within normal range and do not indicate respiratory failure.
❌ C. pH 7.49, PCO₂ 30, PaO₂ 96, HCO₃ 28
Incorrect. This indicates alkalosis, not acute respiratory failure with CO₂ retention.
❌ D. pH 7.50, PCO₂ 44, PaO₂ 93, HCO₃ 34
Incorrect. This is more consistent with metabolic alkalosis.
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NCLEX Pearls
✅ Acute respiratory failure can cause hypoxemia and hypercapnia.
✅ CO₂ retention causes respiratory acidosis.
✅ Respiratory acidosis = low pH + high PaCO₂.
✅ HCO₃⁻ may remain normal in acute respiratory acidosis.
✅ Monitor oxygenation, ventilation, respiratory effort, and mental status.
Memory Trick
“Respiratory failure traps CO₂.”
Final Answer: ✅ A. pH 7.29, PCO₂ 56, PaO₂ 83, HCO₃ 22
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