Carbon Dioxide – CO2 – is poisonous at high levels; but at low levels, it can support vasodilation. The nice thing about CO2 is that you produce it all the time. Just don’t exhale as much CO2 or inhale as much oxygen, and you will raise your CO2 levels. The body carefully controls these, but you may be able to get some benefit from this.
Once again, I am finding that our medical science is quite primitive, and that some ancient forms of health knowledge – such as yoga and Chinese medicine – may have answers that we are only now discovering. I support Western medicine, but when it comes to something as simple as breathing, we simply haven’t had much interest in this field. However, the more I look into breathing, the more I realize that most people either hyperventilate – breathe in too much oxygen – or don’t expand their lungs fully. So, I am researching this and will report more in the near future.