What are the percentage ratio of oxygen and carbon dioxide during inspiration and expiration?

Answer 1

At the alveolar level, the percentages of gases inspired are:

13.7% O2, 5.2% CO2, and 74.9% N2. This is due to the amount of air left in the lungs after inspiration and expiration at tidal volume. If inspiration is strengthened, then this will make the percentage clean up, but not enough to fall within the percentages of Dalton's Law which gives inspired atmospheric air the following percentages:

O2 20.9%, CO2 0.4%, N2 78.6%.

If we look at expired percentages, these are based upon the cellular transfer of gasses from the alveolus to the capillary. Since the capillary is transferring CO2 only, it can be assumed that the entirety of expired air is made of CO2 only. This cannot be true though. The fact that at tidal volume breathing, there is still static air moving to and from the aveolus with both Oxygen and Nitrogen in the expired mix as well. The following percentages from lecture notes are as follows for expired air:

O2 15.8%, CO2 3.55%, N2 74.5%. Remember, these numbers are at the alveolus level, not at the atmospheric level.

I am a Medical Technologies STUDENT. This information is pulled directly from my studies. IF you are a professor and would like to edit my answers for mistakes, feel free, but please document it in the change as a courtesy. My next lab will be testing for these gasses upon inspiration and expiration, but our numbers will reflect atmospheric data or 'at the mouthpiece' of BIOPAC equipment.