What is the blood pH when the partial pressure of carbon dioxide (PCO2) is 60 mm Hg and the bicarbonate concentration is 18 mmol/L?

To determine the blood pH based on the given partial pressure of carbon dioxide (PCO2) and bicarbonate concentration, it’s important to understand the relationship between these parameters in the context of acid-base balance.

A PCO2 of 60 mm Hg indicates a state of respiratory acidosis, as the normal range is typically around 35-45 mm Hg. This elevated level of carbon dioxide leads to an increase in carbonic acid in the blood, which can lower the pH.

The bicarbonate concentration of 18 mmol/L is below the normal range of approximately 22-28 mmol/L, suggesting a compensatory metabolic acidosis where the body is attempting to reestablish acid-base balance by reducing bicarbonate concentration.

Utilizing the Henderson-Hasselbalch equation, which relates pH, bicarbonate (HCO3-), and carbon dioxide (CO2), we can estimate the pH. In scenarios of respiratory acidosis, the pH typically decreases compared to normal physiological levels.

When plugging these values into the equation, you would find that a pH of 7.10 is supported by the combination of the high PCO2 and low bicarbonate level. This aligns with clinical expectations for blood p