When calibrating a nitrogen analyzer for a nitrogen washout test, what room air concentration should be expected?

In a nitrogen washout test, the primary goal is to assess the ventilatory function and the distribution of ventilation within the lungs. During this test, room air serves as a reference, which consists of approximately 78% nitrogen and about 21% oxygen.

When calibrating a nitrogen analyzer, you would expect the analyzer to reflect the concentration of nitrogen present in room air, which is about 78%. This concentration is crucial for establishing a baseline in the nitrogen washout test, as it enables accurate measurement of the nitrogen elimination from the lungs during the washout phase.

In this context, recognizing that room air is primarily composed of nitrogen helps to justify why 78% is the expected concentration. Considering the role of nitrogen in both the ambient air and the physiological processes occurring during pulmonary function testing reinforces the importance of accurate calibration against this known concentration.