Which ABG pattern indicates respiratory acidosis with hypoventilation?

Which ABG pattern indicates respiratory acidosis with hypoventilation?

• A. Low pH with elevated PaCO2; HCO3- may be compensatory if chronic.
• B. High pH with low PaCO2
• C. Low pH with high PaCO2; HCO3- may be compensatory if chronic.
• D. High pH with high PaCO2

Answer: (C)

Respiratory acidosis happens when ventilation is reduced, causing CO2 to accumulate in the blood. CO2 combines with water to form carbonic acid, driving hydrogen ion concentration up and pH down. Therefore, the key ABG clue is a low pH paired with a high PaCO2. The bicarbonate level (HCO3-) will reflect renal compensation: it may rise if the problem is chronic, because the kidneys retain more bicarbonate to buffer the excess acid, whereas in an acute event the HCO3- rise may be minimal. So, a pattern of decreased pH with an elevated PaCO2 indicates respiratory acidosis due to hypoventilation, with HCO3- potentially compensating upward if the condition is long-standing.

Respiratory acidosis happens when ventilation is reduced, causing CO2 to accumulate in the blood. CO2 combines with water to form carbonic acid, driving hydrogen ion concentration up and pH down. Therefore, the key ABG clue is a low pH paired with a high PaCO2. The bicarbonate level (HCO3-) will reflect renal compensation: it may rise if the problem is chronic, because the kidneys retain more bicarbonate to buffer the excess acid, whereas in an acute event the HCO3- rise may be minimal.

So, a pattern of decreased pH with an elevated PaCO2 indicates respiratory acidosis due to hypoventilation, with HCO3- potentially compensating upward if the condition is long-standing.