There is some early data describing a favorable adverse event profile with nitrous oxide as a single agent in adults. Hennequin et al. demonstrated support for the efficacy of nitrous oxide with no major adverse cardio respiratory events. Although approximately 10% of participants received mild gastrointestinal and behavioral side effects (e.g. agitation). Greater than 90% of the study participants stated they would receive nitrous oxide again. In a large prospective trial, Babl et al. found there to be only 2 patients out of 655 who suffered serious adverse events (i.e., chest pain and oxygen desaturation). Both patients had been administered 70% nitrous oxide compared to the more conservative 50% concentration. Additionally, there was an increased incidence of minor adverse events (i.e., emesis and agitation) with the higher concentration of nitrous oxide. Kariman et al. compared nitrous oxide versus parental fentanyl as an analgesic after long bone fracture and found similar pain scores and a more rapid decrease in the pain score in the nitrous oxide group when compared with the opiate group.