What are the three typical parameters tested for when performing an arterial blood gas analysis?

• A. pH, PCO2, PO2
• B. pO2, pCO2, O2 saturation
• C. pH, bicarbonate, lactate
• D. pH, PO2, oxygen content

Answer: (A)

Arterial blood gases are used to assess acid-base balance and how well the lungs are delivering oxygen to the blood. The three main values reported are the blood pH, the partial pressure of carbon dioxide (PaCO2), and the partial pressure of oxygen (PaO2). The pH tells you whether the blood is acidic or basic. PaCO2 reflects the ventilatory component; high levels tend to make the blood more acidic (respiratory acidosis) and low levels tend to make it more basic (respiratory alkalosis). PaO2 indicates oxygenation status; low PaO2 signals hypoxemia and impaired oxygen delivery. Together, these three values provide a quick snapshot of acid-base status, ventilation adequacy, and oxygenation. While bicarbonate and oxygen saturation are also useful, the trio of pH, PaCO2, and PaO2 is the standard set evaluated first.