O₂ consumption. (VO₂)

О2 consumption per minute is related with the state of pulmonary circulation, systemic circulation, liver, kidneys, and gastrointestinal tract. The triiodothyronine activity has primary meaning in the oxygen consumption per minute.

VO2 means oxygen consumption and usually refers to the volume of oxygen consumed in 1 minute.

The following is written in the context of VO2 measurements for fitness or athletic evaluation. Clinical VO2 testing most often involves the monitoring of EKG and other physiologic indices,

and the reason for the test most likely will be to assist in diagnosis of disease or measurement

of disability or progress of rehabilitation.

The air we breathe contains roughly 21% oxygen (O2), 78% Nitrogen (N2) and various trace gases, such as Argon, Carbon Dioxide (CO2) and a few more.

So we inhale 21% O2 and exhale, typically, 17%O2 and about 4% CO2. We have consumed, "burnt", metabolized roughly 4% oxygen. Of course, nothing is ever that simple, because the first part of your exhalation is the very last part of your inhalation. So it is still nearly 21% O2, but then as the source of exhaled gas comes from deeper in the lungs, it contains more and more CO2, and less and less O2. This change in gas concentration occurs rapidly, and the precise measurement requires some sophisticated instruments.

Now to calculate VO2, a simplified equation might look like this:

VO2 = VE x (O2inspired - O2expired)

In plain language, this means VO2 equals the total volume of gas exhaled in 1 minute (VE) multiplied by the difference between inhaled and exhaled oxygen.

So if you exhaled a total of 10 liters of gas during 1 minute, and your mixed exhaled O2 is measured at 17%, then

VO2 = 10 x (0.21 - 0.17)

(Note that 21% and 17% must be written as a fraction,

which is 0.21 and 0.17)

simplified to: VO2 = 10 x 0.04 = 0.4

so your VO2 in this example would be 0.400 liters (or 400 milliliters) per minute, which is close to typical for a person at rest.

https://www.vacumed.com/zcom/newsletter/NewsDetail.do?compid=27&newsid=231

https://www.adinstruments.com/support/knowledge-base/how-calculate-vo2-and-vco2-channel-calculation

https://www.tribelocus.com/find/videos/education/oxygen-uptake-during-exercise/