Did I faint from nitrous oxide due to my cold?

My friend recently had four teeth pulled. His blood pressure was at 169/97, so they put him on nitrous oxide. He fainted. The doctors say they can NOT attribute this to nitrous oxide. He had Claritin in his system at the time, and had a stuffy nose. Could a stuffy nose (or having taken Claritin) make one easily faint after being on nitrous oxide (50 percent nitrous oxide, 50 percent oxygen) for only 20 seconds, then fainting?

[Jerome Bogin, D.D.S.]

There is a number of things that might have contributed to your friend fainting                    and it would be inappropriate for me to try to diagnosis the reason without knowing the patient.