What effect results from exposing a normal arterial blood sample to room air?

Exposing a normal arterial blood sample to room air leads to the absorption of oxygen from the atmosphere and the release of carbon dioxide. When air with a higher concentration of oxygen is introduced to the blood sample, the partial pressure of oxygen (PO2) increases due to the equilibrium of gases between the air and the liquid phase in the blood.

Furthermore, as oxygen is absorbed and carbon dioxide (PCO2) is driven out, the partial pressure of carbon dioxide decreases. This increased oxygen content and decreased carbon dioxide concentration also affects the pH of the sample. The reduction in carbon dioxide results in a lower concentration of carbonic acid, which increases the pH of the blood sample (making it more alkaline).

Therefore, the outcome of these changes is characterized by an increase in PO2, a decrease in PCO2, and an increase in pH, aligning perfectly with the provided answer.