there is indeed a contraindication of oxygen:
For a normal person, our bodies are triggered to breath by the levels of carbon dioxide detected in our blood by the brain. As funny as it may sound, our bodies are actually breathing to remove the carbon dioxide, not to get new oxygen. However, in many patients who have COPD, the body get used to the high levels of the carbon dioxide and there is nothing to trigger their bodies to breath. Therefore, it is the lower oxygen levels that cause these patients to breath.
So, giving these patients oxygen could actually cause them to stop breathing all together, which would no doubt be a contraindication!