Which of the following statements is true regarding the wash-in/wash-out method for performing xenon ventilation studies?

The wash-in/wash-out method for performing xenon ventilation studies involves introducing xenon gas into the lungs to assess pulmonary ventilation. During the wash-in phase, it is essential for the patient to re-breathe a mixture of xenon and oxygen. This process ensures that xenon, which is a non-toxic inert gas, effectively mixes with the air present in the alveoli and provides accurate measurements of lung ventilation.

In this phase, the addition of oxygen facilitates sufficient oxygenation of the patient while enabling the xenon to be absorbed by the lung tissue. Oxygen helps maintain the patient's respiratory function and comfort throughout the procedure. This aspect is crucial for the accuracy of the test since the outcome depends on both the xenon’s distribution in the lung and the preservation of adequate oxygen levels in the patient.

The other options do not accurately reflect the procedure's requirements or implications, highlighting the unique role of oxygen in the wash-in phase. Therefore, option B reflects a true and necessary component of conducting xenon ventilation studies effectively.