What acid/base imbalance is indicated by a pH of 7.53 and decreased PaCO2?

A pH of 7.53 indicates a state of alkalosis, as the normal range for blood pH is typically between 7.35 and 7.45. In this instance, the elevated pH is accompanied by a decreased partial pressure of carbon dioxide (PaCO2).

In respiratory physiology, carbon dioxide is produced as a byproduct of metabolism and is expelled through respiration. A decreased PaCO2 suggests that the body is expelling carbon dioxide more rapidly than it is being produced, which can occur in conditions like hyperventilation. As carbon dioxide combines with water to form carbonic acid, its reduction leads to a decrease in acidity and subsequently raises the pH, resulting in respiratory alkalosis.

Therefore, the combination of an elevated pH and decreased PaCO2 clearly indicates that the body is experiencing respiratory alkalosis, confirming the selection of this option.