A nurse reviews the arterial blood gas (ABG) values of a client admitted with pneumonia: pH, 7.32; PaCO2, 48 mm Hg; PaO2, 70 mm Hg; and HCO3, 24 mEq/L. What do these values indicate?
A.
Metabolic Acidosis
B.
Respiratory Acidosis
C.
Metabolic Alkalosis
D.
Respiratory Alkalosis
The Correct Answer and Explanation is:
The correct answer is B. Respiratory Acidosis.
Explanation:
Arterial blood gas (ABG) analysis is a critical tool in assessing a client’s acid-base balance and respiratory status. To interpret the ABG values, let’s break down the key components and their normal ranges:
- pH: Normal range is 7.35–7.45. A pH below 7.35 indicates acidosis, while a pH above 7.45 indicates alkalosis. In this case, the client’s pH is 7.32, which is lower than the normal range, indicating acidosis.
- PaCO2 (partial pressure of carbon dioxide): Normal range is 35–45 mm Hg. PaCO2 reflects respiratory function. When PaCO2 levels are elevated (>45 mm Hg), it indicates retention of carbon dioxide, suggesting respiratory acidosis. In this case, the client’s PaCO2 is 48 mm Hg, which is higher than the normal range, supporting the diagnosis of respiratory acidosis.
- PaO2 (partial pressure of oxygen): Normal range is 80–100 mm Hg. PaO2 reflects oxygenation status. The client’s PaO2 is 70 mm Hg, indicating mild hypoxemia, which is common in respiratory conditions like pneumonia.
- HCO3 (bicarbonate): Normal range is 22–26 mEq/L. HCO3 reflects the metabolic (renal) component of acid-base balance. In this case, the HCO3 level is 24 mEq/L, which is within the normal range, indicating no compensation by the kidneys.
In respiratory acidosis, the primary issue is the inability of the lungs to effectively remove carbon dioxide (CO2), leading to its accumulation. The elevated PaCO2 is the hallmark of respiratory acidosis. In this case, the pneumonia is causing impaired gas exchange in the lungs, leading to retention of CO2 and reduced oxygenation (low PaO2).
Given the unremarkable bicarbonate (HCO3) level, this represents uncompensated respiratory acidosis. Compensation occurs when the kidneys increase bicarbonate retention to buffer the excess CO2, which has not occurred yet in this client.
Conclusion:
The client’s ABG values indicate uncompensated respiratory acidosis due to the elevated PaCO2, reduced pH, and normal bicarbonate level, consistent with pneumonia’s impact on gas exchange.