What causes carbon monoxide poisoning to cause vomiting?

Lack of oxygen: It is the lack of usuable oxygen to your tissues. The hemoglobin in your red blood cells bind the carbon monoxide but it sticks so strongly that it cannot get unloaded in the tissues where it's needed. Your organs then go into anaerobic (without oxygen) metabolism and the waste product is lactic acid. This as well adds to the vomiting.