If you're refusing to wear a mask due to concerns your brain won't get enough oxygen, I think that ship has already sailed.
While wearing a mask does slightly reduce oxygen levels, that's not why I refuse to wear them.
I refuse to wear masks, mostly because:
[1] It is a violation of my right to make my own healthcare decisions. (ie, it is unconstitutional)
[2] Masks do not stop/prevent the spread of viruses. (ie, wearing a mask for this purpose is pointless)
[3] I do not have covid, thus I cannot spread covid to anyone. (ie, wearing a mask for this purpose is pointless).
There's no way for me to leave my Christian faith out of this explanation of what we are doing to ourselves, so take it for what you feel it's worth.
I do not wish to condone tyranny of any form. I instead promote the exercise of self-governance under God (the ability to govern oneself from within and "be free" rather than being externally governed over and being "a slave"). If one is unwilling/unable to self-govern, then one is asking to be a slave, asking to be ruled over.
The United States of America was truly the greatest nation on Earth, as it was originally founded. It has unfortunately slowly slipped away since then, as its citizenry have collectively decided to shift away from what made it great to begin with. What am I talking about?
As a Christian, I am a believer in self-governance under God. In other words, one has the free will to submit to the law of God. The classic "Garden of Eden" story is a great illustration of how this worked. God gave the law to Adam (to oversee his creation, but to not eat from a particular tree). Adam at this point was to practice self-governance, to willingly submit to God and his law. God did not place any guards or anything around the tree to stop Adam from eating of it. He simply trusted Adam to not eat of it. He allowed Adam the ability to govern over himself, to make his own choice as to whether he would submit to God or not. After Adam chose to not submit to God, God then placed guards around the Garden, banishing Adam from it. Adam was now being externally governed over since he was unable to govern himself inwardly. This sets the model for how we have widely seen governance implemented here on Earth. When people are incapable of inwardly governing themselves, they must be externally governed over. When people can no longer be trusted, they must be restrained.
God's nation of Israel, as recorded in The Bible when it was first founded, was founded on the same basis of self-governance under God. They had no King, no Parliament, no President, etc. to rule over them, but rather, they were only ruled by God's law. Eventually, they failed to self-govern, so God eventually allowed other nations to rule over them, and when oppressed, Israel would turn back to God and God would deliver them from their oppressors via "judges" ('military generals' of sort). After that pattern repeated, Israel asked God to "be like other nations" and to be ruled over by a King. In other words, they were rejecting God as their King and asking to be made slaves under earthly kings. God, after first warning them as to what harm they would be doing to themselves, and Israel ignoring those warnings, granted them their wish. Israel wished to be as gods, determining for themselves what was good and what was evil rather than living under God. They thought that this was giving them freedom/joy, but it was really giving them slavery/oppression. This is precisely what you and I do each and every time we refuse to be governed by the Word of God in our daily lives.
Now, back to the USA, the USA was founded under these same Judeo-Christian self-governance principles that I have explained. The USA was, as we say in our Pledge of Allegiance, "one nation, under God". The citizens of the USA were free people, as the Constitution allowed people the freedom to govern over themselves so long as they kept willingly submitting to it (and in extension to God). However, like the nation of Israel, the USA has also been turning away from these self-governance principles (and turning away from God). Like Israel, the USA will be given over to its enemies and the citizenry of it will feel oppression and beg to be spared from it, shadowing the pattern written about the nation of Israel in the book of Judges.
There really is nothing new under the sun... We are a nation that is no longer willingly submitting to our Constitution (nor to God), and we are now going to be turned over to oppression/slavery as a result of it. The sort of medical tyranny that we are currently seeing with regard to mask wearing and vaccines is only a small portion of what has already occurred and what is still to come. As we are currently seeing, people as of right now think that these are wonderful ideas, as the nation of Israel thought in the Book of Judges, that they'd rather "have a King" (and be externally ruled over, be oppressed slaves) than to allow God to be their King (and be inwardly ruled, be free people).
There is nothing new under the sun.