All of the Following Gases May Be Used as a Tracer

Question

All of the following gases may be used as a tracer gas when performing the DLCO test except:
A) Methane
B) Neon
C) Carbon dioxide
D) Helium

Accepted Answer

Carbon dioxide is not used as a tracer gas in the DLCO (Diffusing Capacity of the Lungs for Carbon Monoxide) test because it is a product of metabolism and is already present in high concentrations in exhaled air. The test aims to measure how well gases can diffuse through the lung barrier, and using a gas that is already a significant component of exhaled air would not provide useful information. Methane, neon, and helium are all inert gases that are not normally present in significant amounts in the body, making them suitable as tracer gases.