What physiological change might be monitored in a patient receiving high concentrations of O2?

The correct choice relates to an important phenomenon observed in patients receiving high concentrations of oxygen. When a patient is administered high levels of oxygen, particularly for extended periods, the body can experience changes in respiratory function, including a decrease in vital capacity. This decrease can occur due to several factors, including the potential development of oxygen toxicity or absorption atelectasis, where nitrogen is washed out of the alveoli, leading to collapse of the alveoli and reduced lung volume capacity.

Monitoring vital capacity is essential because it provides critical information about lung function and can indicate whether a patient is developing complications associated with high oxygen therapy. In contrast, while other physiological parameters like exhaled CO2, lung compliance, and tidal volume can also be affected by oxygen therapy, the direct association with a decrease in vital capacity is particularly significant and commonly monitored in clinical practice to ensure patient safety and effective management of oxygen therapy.