What is the composition of the special diffusion gas mixture used in pulmonary function tests?

The special diffusion gas mixture used in pulmonary function tests typically consists of a very low concentration of carbon monoxide (CO) because it is utilized to assess the diffusing capacity of the lungs for carbon monoxide (DLCO). The mixture is designed to include a specific percentage of oxygen (O2) along with nitrogen (N2) to make up the total volume.

In this context, a composition of 0.3% CO, 21% O2, and the balance being nitrogen is accurate as it reflects the typical composition used in clinical settings. The low level of carbon monoxide is crucial because it allows for safe testing while still providing effective measurement of gas exchange efficiency in the alveoli. The presence of nitrogen is necessary to fill the remaining portion of the gas mixture and maintain appropriate atmospheric conditions during testing.

The percentage of oxygen included in the mixture is also significant, as this provides a standard environment for the measurements. Therefore, having 21% O2 aligns with the ambient air atmosphere, ensuring that the results of the diffusion test are valid and comparable to normal physiological conditions.

This specific combination ensures effectiveness and safety in assessing pulmonary function through diffusion capacity tests.