An ABG is drawn on 71-year-old patient with a history of chronic COPD. After reviewing the patient’s ABG results, which of the following values would be most reflective of the severity of the patient's chronic condition?

This one is a little tricky. Since the question tells us that the patient has chronic COPD, that means that they are a CO2 retainer. So with that said, we should expect their PaCO2 levels to be increased.

So in this case, the arterial Bicarb level is actually most reflective of chronic CO2 retention. With an increased PaCO2, the body will compensate by increasing the amount of Bicarb in order to get the pH back into the normal range.

The pH, PaCO2, and PaO2 values tell us more about the patient's acute condition — whereas the question is asking about the patient’s chronic condition. So now we know that the correct answer has to be C.

 The correct answer is: C. HCO3-