Question 1

What are normal ABG values?

Accepted Answer

Common adult reference ranges are pH 7.35 to 7.45, PaCO2 35 to 45 mmHg, HCO3 22 to 26 mEq/L, PaO2 80 to 100 mmHg, and SaO2 at least 95 percent.

Question 2

How do you calculate the P/F ratio?

Accepted Answer

Divide PaO2 by FiO2. A PaO2 of 90 on FiO2 0.40 gives a P/F ratio of 225. Values below 300 suggest impaired oxygenation.

Question 3

What is respiratory acidosis?

Accepted Answer

Respiratory acidosis occurs when pH is low and PaCO2 is elevated, usually because the patient is not ventilating enough to eliminate carbon dioxide.

Question 4

Why can pulse oximetry look normal in carbon monoxide poisoning?

Accepted Answer

Standard pulse oximetry cannot reliably distinguish oxyhemoglobin from carboxyhemoglobin. Co-oximetry is needed to accurately measure hemoglobin fractions.

ABG Interpretation TMC Questions