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Nursing QUESTION #9224
Question 1
A patient in the ICU has the following arterial blood gas (ABG) results: \(\text{pH} = 7.28\), \(\text{PaCO}_2 = 55 \text{ mmHg}\), \(\text{HCO}_3^- = 24 \text{ mEq/L}\), \(\text{PaO}_2 = 70 \text{ mmHg}\). Which acid-base disorder is present?
  • Metabolic acidosis with respiratory compensation
  • Respiratory acidosis — uncompensated✔️
  • Metabolic alkalosis with respiratory compensation
  • Mixed respiratory and metabolic alkalosis
Correct Answer Explanation
Correct Answer: B — Respiratory acidosis, uncompensated

Step-by-step ABG interpretation:
  1. pH: \(7.28 < 7.35\) → Acidosis
  2. PaCO\(_2\): \(55 > 45 \text{ mmHg}\) → Respiratory cause (CO\(_2\) is an acid; elevated = acidosis)
  3. HCO\(_3^-\): \(24 \text{ mEq/L}\) → Normal (22–26 mEq/L) → No metabolic compensation yet
Conclusion: Respiratory acidosis — uncompensated (because HCO\(_3^-\) is still normal, kidneys have not yet retained bicarbonate).

Normal ABG Reference Values:
ParameterNormal Range
pH\(7.35 - 7.45\)
PaCO\(_2\)\(35 - 45 \text{ mmHg}\)
HCO\(_3^-\)\(22 - 26 \text{ mEq/L}\)
PaO\(_2\)\(80 - 100 \text{ mmHg}\)
SaO\(_2\)\(95 - 100\%\)
Common causes in ICU: COPD exacerbation, oversedation, neuromuscular disease, pneumothorax.