What I hope is that it will also be the case for SN
Mostly carbon dioxide (C02) dissolves out of your cells and into your red blood cells. Once C02 enters the red blood cells a small amount (about 10% of the total) binds hemoglobin to form carbaminohemoglobin. The vast majority of the C02 (around 90%) interacts with water within the red blood cells to form carbonic acid which is transported to the lungs where it diffuses through capillaries in the alveoli and is then exhaled as C02 gas.
Carbon dioxide does
not interact with the iron/heme in the hemoglobin, which is the part of hemoglobin that SN changes to turn it into methemoglobin, so I would assume the 10% of C02 that binds with hemoglobin and forms into carbaminohemoglobin would still be able to do so with methemoglobin, but I was unable to find any data on that. Still, even if it can't, 90% of carbon dioxide would still diffuse naturally into the blood to form carbonic acid and be transported to the lungs to be exhaled because SN does not interfere with that process.
I hope that made sense.
Don't wanna be a killjoy, but this type of hypoxia and anemic hypoxia, which methemoglobinemia falls under, feel very different.
Not saying SN isn't peaceful, it just shouldn't be compared to inert gas asphyxiation.
You are correct, the example in the video is Hypoxemic hypoxia and what SN causes is anemic hypoxia. This is the first I've heard of the 4 different kinds of hypoxia having different symptoms though. Usually the symptoms are are the same for all 4 such as here:
https://my.clevelandclinic.org/health/diseases/23063-hypoxia
For me it makes sense that the symptoms should at least be similar as they're all just ways that cause your cells to not get enough oxygen, no?