why is carbon monoxide used to test how lungs are working,by measuring gas transfer?

Answer 1

That's news to me.

Carbon monoxide is produced by incomplete combustion of carbon. It is absorbed in to the blood stream much more readily than oxygen thus disabling the hemoglobin.

Its a pretty dangerous way to test gas absorption. Are you sure you have that right?

Answer 2

Sort of. The lungs do two main things:
[1] transfer oxygen (O2) to the blood
[2] remove carbon dioxide (CO2) and monoxide (CO) from the blood

Thus, a measure of how much CO and CO2 is exhaled is also a measure of lung function.

"Carbon monoxide diffusing capacity (also called transfer factor, or TF), which measures how well your lungs transfer a small amount of carbon monoxide (CO) into the blood. Two different methods are used for this test. If the single-breath or breath-holding method is used, you will take a breath of air containing a very small amount of carbon monoxide from a container while measurements are taken. In the steady-state method, you will breathe air containing a very small amount of carbon monoxide from a container. The amount of carbon monoxide in your arterial blood is then measured. Diffusing capacity provides an estimate of how well a gas is able to move from your lungs into your blood."