What effect does prolonged storage have on arterial blood gas results?

Prolonged storage of arterial blood gas samples can negatively impact the accuracy of the results, particularly by decreasing both pH and PO2. This occurs due to several biochemical processes that take place after the sample is drawn, especially if the sample is not properly processed or stored.

When arterial blood is stored for an extended period before analysis, a few key changes happen. First, there is a shift towards anaerobic metabolism, leading to the production of lactic acid. The accumulation of lactic acid contributes to a decrease in pH because it increases the acidity of the sample. In addition, the cells within the blood sample consume oxygen over time, leading to a decline in PO2 levels. As cells use up the oxygen, the partial pressure of oxygen detected will be lower than the actual value at the time of collection.

Thus, the correct answer highlights the relationship between prolonged storage and changes in pH and PO2, indicating that both are adversely affected and pointing towards a deterioration in the sample's integrity and the reliability of the results derived from it.