pH 7.24, PaO2 55 mm Hg, PaCO250 mm Hg, HCO3-30 mEq/L consistent with:
**Core Concept**
The given arterial blood gas (ABG) values indicate a metabolic acidosis with a compensatory respiratory component. The pH is decreased, PaCO2 is elevated, and HCO3- is also elevated, pointing towards a mixed acid-base disorder.
**Why the Correct Answer is Right**
The metabolic acidosis is due to the elevated HCO3- levels, which is consistent with a non-respiratory acidosis. The respiratory component is indicated by the decreased PaO2 and elevated PaCO2, suggesting hyperventilation. However, the PaO2 is not significantly low, making it less likely a severe respiratory acidosis. The combination of metabolic acidosis and mild respiratory alkalosis is consistent with a compensated respiratory alkalosis.
**Why Each Wrong Option is Incorrect**
**Option A:** A severe respiratory acidosis would have a higher PaCO2 and a lower pH, which is not consistent with the given values.
**Option B:** A severe metabolic alkalosis would have a lower HCO3- level and a higher pH, which is not consistent with the given values.
**Option C:** A severe respiratory alkalosis would have a lower PaCO2 and a higher pH, which is not consistent with the given values.
**Clinical Pearl / High-Yield Fact**
In ABG interpretation, the first step is to identify the primary acid-base disorder, and then look for compensatory mechanisms. Remember that a compensatory response does not necessarily mean the patient is "normal."
**Correct Answer: C. Metabolic acidosis with a compensatory respiratory alkalosis.**