Friday, 16 September 2011

Sucking Fumes

OK, just to prove that my sabbatical has not been non-stop fun and games, here's a new technique I'm learning for measuring total hemoglobin (the molecule in your blood that actually carries oxygen) mass here in Finland. The principle is to use carbon monoxide (CO) rebreathing, where you use CO as a "tracer" in your body. A tracer is a substance that normally is not in the body, so that it can be easily detected and distinguished from what is normally already in your body.

CO works well as a tracer because it has a really high affinity for binding to hemoglobin (the same site where oxygen normally binds, which is why CO poisoning can be lethal), and it normally is at (hopefully) a pretty minimal level in your body. Lots of baseline testing has also given a time course for the rate at which CO is taken up by the body and the rate at which it binds to hemoglobin. Therefore, if you breathe in a known volume of the gas and let it settle in your body, and take blood samples before and after at a set time, then the amount of CO in the blood sample is a good estimation of the total hemoglobin in your body. The amount of CO is based on your sex, size, and fitness, but is usually at a level less than 1 cigarette (66 mL in my case).

You also need to measure how much CO is in your expired breath too at these time points, so that you can subtract the amount of CO that hasn't gotten into your bloodstream. The "rebreathing" comes from the fact that you breathe in and out of a small 3 L bag of pure oxygen for the 2 min, which the CO is mixed into. The rebreathing is needed to make sure you breathe in the CO without it escaping.

The most important thing with this test is that it clearly demonstrated my absolute lack of athletic potential, as getting any performance is like squeezing blood from the proverbial stone given my ridiculously low hemoglobin results!