Juvenile dermatomyositis
2.2. Diffusion of CO
It is a test that will measure the gas exchange that takes place in the lungs and will provide information about the diffusion process. This process is necessary for the oxygen (O2) that we breathe in to pass into the blood and to eliminate the carbon monoxide (CO) produced by our body.
It is used to diagnose certain lung diseases and to monitor or follow up the evolution of people with lung disease.
To perform the test, the patient must first take a few quiet breaths, followed by a maximum exhalation and maximum inspiration (in that order) to inhale air containing a mixture of carbon monoxide and a tracer gas, which can be methane or helium. After that, the air must be held for about 10 seconds and then quickly expelled. At the end of the test, the tracer gas exhaled is analysed to see how much of it was absorbed during breathing. Typically it is between 80 and 120% of the reference values.
Like spirometry, it requires the cooperation of the patient.